CMakeLists: Bump minimum macOS to 11.0

[OatmealDome]

Bumps the minimum macOS version to 11.0 Big Sur. I've also gone ahead and removed some checks for macOS 10.15 which were missed when the last version bump happened.

Approximately ~2.6% of our macOS users within the past 30 days (and have analytics enabled) are running a version of macOS 10.15 Catalina.

Analytics data

macOS Version	Unique Users
15.5.0	1
15.4.0	571
15.3.2	4484
15.3.1	4869
15.3.0	626
15.2.0	802
15.1.1	560
15.1.0	411
15.0.1	304
15.0.0	265
14.7.5	4
14.7.4	247
14.7.3	67
14.7.2	67
14.7.1	74
14.7.0	70
14.6.1	917
14.6.0	195
14.5.0	905
14.4.1	323
14.4.0	169
14.3.1	113
14.3.0	155
14.2.1	163
14.2.0	37
14.1.2	43
14.1.1	66
14.1.0	58
14.0.0	102
13.7.5	12
13.7.4	420
13.7.3	55
13.7.2	61
13.7.1	72
13.7.0	29
13.6.9	37
13.6.8	2
13.6.7	60
13.6.6	43
13.6.5	4
13.6.4	17
13.6.3	22
13.6.2	2
13.6.1	24
13.6.0	15
13.5.2	27
13.5.1	51
13.5.0	102
13.4.1	58
13.4.0	111
13.3.1	59
13.3.0	37
13.2.1	110
13.2.0	20
13.1.0	49
13.0.1	40
13.0.0	121
12.7.6	949
12.7.5	117
12.7.4	146
12.7.3	30
12.7.2	19
12.7.1	21
12.7.0	10
12.6.9	4
12.6.8	10
12.6.7	23
12.6.6	14
12.6.5	22
12.6.4	5
12.6.3	23
12.6.2	7
12.6.1	15
12.6.0	37
12.5.1	43
12.5.0	65
12.4.0	46
12.3.1	27
12.3.0	24
12.2.1	43
12.2.0	8
12.1.0	34
12.0.1	47
12.0.0	2
11.7.10	412
11.7.9	12
11.7.8	9
11.7.7	7
11.7.6	3
11.7.5	2
11.7.4	10
11.7.3	1
11.7.2	3
11.7.1	3
11.7.0	6
11.6.8	1
11.6.7	3
11.6.6	1
11.6.5	2
11.6.4	4
11.6.3	1
11.6.2	5
11.6.0	23
11.5.2	14
11.5.1	8
11.5.0	2
11.4.0	16
11.3.1	9
11.3.0	5
11.2.3	18
11.2.2	4
11.2.1	7
11.2.0	6
11.1.0	10
11.0.1	7
11.0.0	1
10.16.0	483
10.15.7	530
10.15.6	9
10.15.5	7
10.15.4	4
10.15.3	7
10.15.2	2
10.15.1	2
10.15.0	5
10.14.6	67
10.14.5	2
10.14.2	1
10.13.6	153
10.13.3	2
10.13.1	5
10.13.0	4
10.12.6	22
10.12.5	1
10.12.3	1
10.11.6	3
10.9.5	2

[dolphin-ci]

FifoCI detected that this change impacts graphical rendering. Here are the behavior differences detected by the system:

• last-story-shadows on mvk-osx-m1: diff
• f-zero-rain on mtl-osx-m1: diff

_{^{automated-fifoci-reporter}}

[MayImilae]

What benefits does bumping the spec bring in this case?

Generally 2% is a little more than I'd like for a cutoff. However, that's 2% of our macOS users which make up about a percent of our userbase, so in total this affects a very small number of our total users. So I'm not opposed to this, but I am curious about what we gain from this move.

Also this finally cuts off my 2012 macbook pro from the latest Dolphin builds. At least, unless I get creative.

[jordan-woyak]

What benefits does bumping the spec bring in this case?

I was pushing for a macOS spec bump for a Common::Event performance improvement in #13475

It would also allow for a Qt version bump.

Also, even macOS 12 is EOL. Apple doesn't support macOS 10, why should we. :P

[OatmealDome]

It also looks like Dolphin is currently broken on 10.15 due to PR #13269: https://bugs.dolphin-emu.org/issues/13743. I've unfortunately had to leave it broken due to my lack of a testing environment.

[JMC47]

If it's broken anyway, perhaps we should merge this and if a work-around is found we can always revert it?