Replace PCRE1 with PCRE2

[Lpsd]

Summary

Replaces the outdated PCRE1 with PCRE2 10.47 from https://github.com/PCRE2Project/pcre2

With the exception of a startup check in Server/mods/deathmatch/logic/CGame.cpp, the only usage of PCRE is for the Lua implementation of pregFind, pregMatch and pregReplace functions. A testing resource is provided below with 40 test cases.

There is no C++ wrapper in PCRE2, so we now have our own under Shared/pcrecpp_compat.h

Motivation

PCRE1 is not maintained anymore

Test plan

Test resource: pcre.zip
Simply start the resource and all 40 tests will run with results output in console (server).

It's worth noting that 5 of the tests don't actually work with PCRE1, however they are resolved in PCRE2 -- or rather by the new C++ wrapper. This isn't a concern for backwards compatibility since these cases weren't working properly (or at all) previously.

#	Function	Test	Expected	PCRE1	PCRE2
10	pregFind	"line1\nline2" / "^line2" / "m"	true	❌	✅
13	pregFind	"a\nb" / "a.b"	false	❌	✅
16	pregFind	"Γειά" / "\w+" / "u"	true	❌	✅
27	pregMatch	"John Doe" / "(\w+) (\w+)"	{"John Doe"}	❌	✅
35	pregReplace	"a/b" / "/" / "\"	"a\b"	❌	✅

• 10, 13 - Old pcrecpp wrapper failed to pass PCRE_MULTILINE / PCRE_DOTALL flags through to pcre_compile. The C API supported them, but the C++ wrapper silently dropped them.
• 16 - Old set_utf8(true) only set PCRE_UTF8 without PCRE_UCP, so \w matched only ASCII even with UTF-8 enabled. Our compat wrapper correctly enables both PCRE2_UTF + PCRE2_UCP.
• 27 - Old FindAndConsume returned only the first capture group ("John") instead of the full match ("John Doe") for patterns with parenthesized groups.
• 35 - Old pcrecpp used \ for backreferences in replacement strings, causing a literal \ to be consumed as an escape. PCRE2's pcre2_substitute uses $ for backreferences, so literal \ passes through correctly.

Checklist

• Your code should follow the coding guidelines.
• Smaller pull requests are easier to review. If your pull request is beefy, your pull request should be reviewable commit-by-commit.