[stdlib] Simplify __SwiftNativeNSArrayWithContiguousStorage.count

[lorentey]

There is what looks like unnecessary levels of indirection in the implementation of NSArray.count on the native Array storage class. Remove it.

[lorentey]

@swift-ci test

[Catfish-Man]

Looks immensely better!

[Catfish-Man]

@swift-ci smoke benchmark

[swift-ci]

Performance: -O

Regression	OLD	NEW	DELTA	RATIO
FlattenListLoop	4709	5186	+10.1%	0.91x (?)
NSStringConversion.Rebridge.Mutable	836	904	+8.1%	0.92x (?)
Improvement	OLD	NEW	DELTA	RATIO
LazilyFilteredArrayContains	36900	33700	-8.7%	1.09x
Array2D	8112	7520	-7.3%	1.08x
RemoveWhereSwapInts	72	67	-6.9%	1.07x (?)
MapReduce	426	397	-6.8%	1.07x
MapReduceAnyCollection	426	398	-6.6%	1.07x (?)

Code size: -O

Performance: -Osize

Improvement	OLD	NEW	DELTA	RATIO
FlattenListLoop	4432	4062	-8.3%	1.09x (?)
Array2D	7216	6624	-8.2%	1.09x (?)
RandomShuffleLCG2	800	736	-8.0%	1.09x
RemoveWhereMoveInts	40	37	-7.5%	1.08x (?)
RemoveWhereSwapInts	67	62	-7.5%	1.08x (?)
MapReduce	433	404	-6.7%	1.07x

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
NSStringConversion.Rebridge.Mutable	889	974	+9.6%	0.91x (?)
Improvement	OLD	NEW	DELTA	RATIO
DictionaryBridgeToObjC_Access	1260	1132	-10.2%	1.11x (?)

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