[ownership] Move OME on the stdlib passed the existential specializer/performance constant prop.

[gottesmm]

Just trying to do this in as small chunks as possible to get better blame
lists.

[gottesmm]

@swift-ci test

[gottesmm]

@swift-ci benchmark

[gottesmm]

@swift-ci test source compatibility

[gottesmm]

@swift-ci test windows platform

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
DictionaryKeysContainsCocoa	32	36	+12.5%	0.89x (?)

Code size: -O

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
StringToDataLargeUnicode	3450	3800	+10.1%	0.91x (?)
Improvement	OLD	NEW	DELTA	RATIO
Diffing.Same	9	8	-11.1%	1.12x (?)

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
String.data.LargeUnicode	218	240	+10.1%	0.91x (?)
DataCreateMediumArray	6660	7240	+8.7%	0.92x (?)

Code size: -swiftlibs

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the
regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false
alarms. Unexpected regressions which are marked with '(?)' are probably noise.
If you see regressions which you cannot explain you can try to run the
benchmarks again. If regressions still show up, please consult with the
performance team (@eeckstein).

Hardware Overview

  Model Name: Mac Pro
  Model Identifier: MacPro6,1
  Processor Name: 12-Core Intel Xeon E5
  Processor Speed: 2.7 GHz
  Number of Processors: 1
  Total Number of Cores: 12
  L2 Cache (per Core): 256 KB
  L3 Cache: 30 MB
  Memory: 64 GB

[gottesmm]

Debug build failed in a java error... IDK.

[gottesmm]

I looked at the source compat failures. They are the same as on the bots, so it isn't this PR.