Remove more unsafe code from Uri internals

[MihaZupan]

Removes unsafe code from CheckCanonical and all its callers.

InternalIsWellFormedOriginalString was also checking the same thing twice, and we also check for it during parsing, so I added a new flag for it to avoid the duplication (SchemeNotCanonical_NoTrailingSlashes).

Reviewing is easier without whitespace diffs.

Draft while I gett more perf numbers.

[dotnet-policy-service]

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[MihaZupan]

@MihuBot benchmark Perf_Uri -long -noTimeLimit

[MihaZupan]

This was a bug in previous logic - since we didn't increment i when encountering a surrogate pair, the next iteration would see an unpaired low surrogate and mark the input as non-iri-canonical.

[MihuBot]

System.Tests.Perf_Uri

BenchmarkDotNet v0.14.1-nightly.20250107.205, Linux Ubuntu 22.04.5 LTS (Jammy Jellyfish)
AMD EPYC 9V74, 1 CPU, 8 logical and 4 physical cores
LongRun : .NET 10.0.0 (42.42.42.42424), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
Job=LongRun  IterationCount=100  LaunchCount=3
WarmupCount=15

Method	Toolchain	input	Mean	Error	P95	Ratio	Allocated	Alloc Ratio
ParseAbsoluteUri	Main	?	165.5719 ns	0.3480 ns	168.7582 ns	1.00	304 B	1.00
ParseAbsoluteUri	PR	?	170.9013 ns	0.3740 ns	173.6986 ns	1.03	304 B	1.00
DnsSafeHost	Main	?	165.1498 ns	1.2993 ns	178.4041 ns	1.00	328 B	1.00
DnsSafeHost	PR	?	166.7840 ns	0.4855 ns	170.9062 ns	1.01	328 B	1.00
BuilderToString	Main	?	70.1461 ns	0.0648 ns	70.7084 ns	1.00	216 B	1.00
BuilderToString	PR	?	72.0784 ns	0.2661 ns	73.8651 ns	1.03	216 B	1.00
UriBuilderReplacePort	Main	?	66.7879 ns	0.2376 ns	68.8186 ns	1.00	216 B	1.00
UriBuilderReplacePort	PR	?	65.9095 ns	0.0750 ns	66.6127 ns	0.99	216 B	1.00
GetComponents	Main	?	10.9271 ns	0.0312 ns	11.2100 ns	1.00	80 B	1.00
GetComponents	PR	?	10.7526 ns	0.0230 ns	10.9198 ns	0.98	80 B	1.00
PathAndQuery	Main	?	0.8668 ns	0.0565 ns	1.8666 ns	1.07	-	NA
PathAndQuery	PR	?	0.7692 ns	0.0229 ns	0.8403 ns	0.95	-	NA
EscapeDataString	Main	{{{{{{{{{{{{(...){{{{{{{{{{{{ [1000]	4,782.3351 ns	4.0869 ns	4,817.0185 ns	1.00	6024 B	1.00
EscapeDataString	PR	{{{{{{{{{{{{(...){{{{{{{{{{{{ [1000]	4,788.0341 ns	6.4869 ns	4,836.9449 ns	1.00	6024 B	1.00
CombineAbsoluteRelative	Main	/new/path	94.1380 ns	0.1055 ns	94.9918 ns	1.00	200 B	1.00
CombineAbsoluteRelative	PR	/new/path	93.9020 ns	0.0476 ns	94.2785 ns	1.00	200 B	1.00
UnescapeDataString	Main	%E4%BD%A0%E5%A5%BD	37.8972 ns	0.1065 ns	38.6942 ns	1.00	32 B	1.00
UnescapeDataString	PR	%E4%BD%A0%E5%A5%BD	37.5308 ns	0.0223 ns	37.7110 ns	0.99	32 B	1.00
EscapeDataString	Main	a{üa{üa{üa{ü(...)a{üa{üa{üa{ü [999]	7,387.2787 ns	9.6952 ns	7,456.3239 ns	1.00	6688 B	1.00
EscapeDataString	PR	a{üa{üa{üa{ü(...)a{üa{üa{üa{ü [999]	7,546.1135 ns	8.6053 ns	7,612.2079 ns	1.02	6688 B	1.00
EscapeDataString	Main	aaaaaaaaaaaa(...)aaaaaaaaaaaa [1000]	26.6628 ns	0.0186 ns	26.7594 ns	1.00	-	NA
EscapeDataString	PR	aaaaaaaaaaaa(...)aaaaaaaaaaaa [1000]	26.3225 ns	0.0215 ns	26.4944 ns	0.99	-	NA
UnescapeDataString	Main	abc%20def%20ghi%20	29.4827 ns	0.0791 ns	29.9335 ns	1.00	48 B	1.00
UnescapeDataString	PR	abc%20def%20ghi%20	30.6707 ns	0.2333 ns	32.5417 ns	1.04	48 B	1.00
Ctor	Main	http://dot.net	50.5849 ns	0.0483 ns	50.8468 ns	1.00	56 B	1.00
Ctor	PR	http://dot.net	50.1904 ns	0.0424 ns	50.5088 ns	0.99	56 B	1.00
CtorIdnHostPathAndQuery	Main	http://dot.ne(...)alue#fragment [43]	184.7182 ns	0.2019 ns	186.7217 ns	1.00	248 B	1.00
CtorIdnHostPathAndQuery	PR	http://dot.ne(...)alue#fragment [43]	192.2427 ns	0.3051 ns	194.6211 ns	1.04	248 B	1.00
Ctor	Main	http://höst.with.ünicode	227.3324 ns	0.3973 ns	230.9932 ns	1.00	256 B	1.00
Ctor	PR	http://höst.with.ünicode	222.4252 ns	1.8804 ns	236.2161 ns	0.98	256 B	1.00
CtorIdnHostPathAndQuery	Main	http://höst.w(...)alue#fragment [53]	1,063.8598 ns	2.5461 ns	1,085.6317 ns	1.00	936 B	1.00
CtorIdnHostPathAndQuery	PR	http://höst.w(...)alue#fragment [53]	1,081.9218 ns	4.2003 ns	1,111.5276 ns	1.02	936 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/	108.6913 ns	0.1150 ns	109.5783 ns	1.00	200 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/	112.0170 ns	0.1612 ns	113.5217 ns	1.03	200 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/p(...)s?key=ünicode [50]	457.3145 ns	1.6727 ns	468.6085 ns	1.00	752 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/p(...)s?key=ünicode [50]	457.0893 ns	0.6682 ns	462.1179 ns	1.00	752 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/p(...)es?key=va lue [49]	277.8531 ns	0.3749 ns	280.7162 ns	1.00	296 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/p(...)es?key=va lue [49]	280.0348 ns	0.1500 ns	281.1408 ns	1.01	296 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/p(...)3&key4=value4 [64]	228.5983 ns	0.1650 ns	230.1201 ns	1.00	304 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/p(...)3&key4=value4 [64]	238.0109 ns	0.4028 ns	240.9209 ns	1.04	304 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/p(...)=%C3%BCnicode [61]	496.7966 ns	0.6181 ns	501.1303 ns	1.00	752 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/p(...)=%C3%BCnicode [61]	511.6140 ns	3.0735 ns	523.6821 ns	1.03	752 B	1.00
CtorIdnHostPathAndQuery	Main	http://host/p(...)?key=va%20lue [57]	227.8241 ns	0.2377 ns	229.6564 ns	1.00	296 B	1.00
CtorIdnHostPathAndQuery	PR	http://host/p(...)?key=va%20lue [57]	231.6233 ns	0.0943 ns	232.3321 ns	1.02	296 B	1.00
Ctor	Main	http://xn--hs(...)n--nicode-2ya [38]	76.0055 ns	0.4043 ns	78.7504 ns	1.00	56 B	1.00
Ctor	PR	http://xn--hs(...)n--nicode-2ya [38]	78.8860 ns	0.9319 ns	87.1759 ns	1.04	56 B	1.00
CtorIdnHostPathAndQuery	Main	http://xn--hs(...)alue#fragment [67]	231.7594 ns	0.2575 ns	233.7422 ns	1.00	296 B	1.00
CtorIdnHostPathAndQuery	PR	http://xn--hs(...)alue#fragment [67]	239.9377 ns	0.3053 ns	241.6685 ns	1.04	296 B	1.00
Ctor	Main	https://a.much.longer.domain.name	86.5454 ns	0.0388 ns	86.8394 ns	1.00	56 B	1.00
Ctor	PR	https://a.much.longer.domain.name	85.7820 ns	0.2609 ns	87.2754 ns	0.99	56 B	1.00
CtorIdnHostPathAndQuery	Main	https://a.muc(...)alue#fragment [62]	235.6889 ns	0.3535 ns	238.5228 ns	1.00	280 B	1.00
CtorIdnHostPathAndQuery	PR	https://a.muc(...)alue#fragment [62]	245.1232 ns	0.6807 ns	250.2221 ns	1.04	280 B	1.00
Ctor	Main	https://contoso.com	49.8830 ns	0.1187 ns	50.7290 ns	1.00	56 B	1.00
Ctor	PR	https://contoso.com	50.6731 ns	0.1768 ns	52.0653 ns	1.02	56 B	1.00
Ctor	Main	https://CONTOSO.com	50.0956 ns	0.0376 ns	50.3699 ns	1.00	56 B	1.00
Ctor	PR	https://CONTOSO.com	50.3606 ns	0.0635 ns	50.7781 ns	1.01	56 B	1.00
CtorIdnHostPathAndQuery	Main	https://conto(...)alue#fragment [48]	186.0344 ns	0.1007 ns	186.9050 ns	1.00	256 B	1.00
CtorIdnHostPathAndQuery	PR	https://conto(...)alue#fragment [48]	197.0772 ns	0.3185 ns	199.2947 ns	1.06	256 B	1.00
CtorIdnHostPathAndQuery	Main	https://CONTO(...)alue#fragment [48]	187.8457 ns	0.2661 ns	189.9762 ns	1.00	256 B	1.00
CtorIdnHostPathAndQuery	PR	https://CONTO(...)alue#fragment [48]	197.6420 ns	0.5129 ns	200.9643 ns	1.05	256 B	1.00
EscapeDataString	Main	üüüüüüüüüüüü(...)üüüüüüüüüüüü [1000]	8,698.8407 ns	5.8625 ns	8,745.8565 ns	1.00	12024 B	1.00
EscapeDataString	PR	üüüüüüüüüüüü(...)üüüüüüüüüüüü [1000]	8,708.0605 ns	6.2922 ns	8,765.3683 ns	1.00	12024 B	1.00