[benchmark] Add another test to floating point conversion benchmark

[xwu]

This PR adds a benchmark to test the performance of the default implementation of BinaryFloatingPoint.init<T>(exactly:) where T: BinaryFloatingPoint.

It is a companion to #33910 and will need to be landed separately in order to demonstrate that the other PR produces the expected performance improvement.

[xwu]

@swift-ci benchmark

[xwu]

@swift-ci test Linux platform

[xwu]

@swift-ci test macOS platform

[xwu]

@swift-ci test macOS platform

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@swift-ci benchmark

[xwu]

@swift-ci test Linux platform

[swift-ci]

Performance: -O

Improvement	OLD	NEW	DELTA	RATIO
Dictionary4	196	150	-23.5%	1.31x
Dictionary4OfObjects	229	184	-19.7%	1.24x
ArrayAppendUTF16Substring	33552	30816	-8.2%	1.09x (?)
ArrayAppendAsciiSubstring	33552	30816	-8.2%	1.09x (?)
ArrayAppendLatin1Substring	34236	31464	-8.1%	1.09x (?)
Added	MIN	MAX	MEAN	MAX_RSS
ConvertFloatingPoint.MockFloat64Exactly	701	701	701	—
ConvertFloatingPoint.MockFloat64Exactly2	1047	1067	1054	—

Code size: -O

Regression	OLD	NEW	DELTA	RATIO
FloatingPointConversion.o	27007	41265	+52.8%	0.65x

Performance: -Osize

Regression	OLD	NEW	DELTA	RATIO
Dictionary4	155	290	+87.1%	0.53x
Dictionary4OfObjects	229	348	+52.0%	0.66x
ConvertFloatingPoint.MockFloat64ToDouble	14	16	+14.3%	0.88x (?)
NopDeinit	9900	11000	+11.1%	0.90x (?)
Improvement	OLD	NEW	DELTA	RATIO
ArrayLiteral2	113	102	-9.7%	1.11x (?)
CharacterLiteralsSmall	226	211	-6.6%	1.07x (?)
Added	MIN	MAX	MEAN	MAX_RSS
ConvertFloatingPoint.MockFloat64Exactly	694	694	694	—
ConvertFloatingPoint.MockFloat64Exactly2	1044	1044	1044	—

Code size: -Osize

Regression	OLD	NEW	DELTA	RATIO
FloatingPointConversion.o	25738	39406	+53.1%	0.65x

Performance: -Onone

Added	MIN	MAX	MEAN	MAX_RSS
ConvertFloatingPoint.MockFloat64Exactly	790	832	807	—
ConvertFloatingPoint.MockFloat64Exactly2	1640	1736	1672	—

Code size: -swiftlibs

✅	Benchmark Check Report
⚠️⏱	ConvertFloatingPoint.MockFloat64Exactly2 execution took at least 1006 μs. Decrease the workload of ConvertFloatingPoint.MockFloat64Exactly2 by a factor of 2 (10), to be less than 1000 μs.

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 mini
  Model Identifier: Macmini8,1
  Processor Name: 6-Core Intel Core i7
  Processor Speed: 3.2 GHz
  Number of Processors: 1
  Total Number of Cores: 6
  L2 Cache (per Core): 256 KB
  L3 Cache: 12 MB
  Memory: 64 GB