[benchmark] Add a basic benchmark for Unicode._CharacterRecognizer

[lorentey]

This measures the performance of the stdlib’s core grapheme breaking algorithm, without any String overhead.

[lorentey]

@swift-ci benchmark

[lorentey]

@swift-ci benchmark

[lorentey]

@swift-ci smoke test

[lorentey]

------- Performance (x86_64): -O -------
ADDED                        MIN       MAX        MEAN                MAX_RSS  
CharacterRecognizer.ascii    63.45     63.45      63.45               —        
CharacterRecognizer.mixed    21.326    21.652     21.43466666666667   —        

------- Performance (x86_64): -Osize -------
ADDED                            MIN        MAX        MEAN                 MAX_RSS  
CharacterRecognizer.ascii        66.524     66.524     66.524               —        
CharacterRecognizer.mixed        21.093     21.465     21.240333333333332   —        

------- Performance (x86_64): -Onone -------
ADDED                                 MIN       MAX       MEAN      MAX_RSS  
CharacterRecognizer.ascii             113.588   113.706   113.647   —        
CharacterRecognizer.mixed             23.667    23.727    23.697    —        

Traceback (most recent call last):
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/run_smoke_bench", line 393, in <module>
    sys.exit(main())
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/run_smoke_bench", line 147, in main
    return test_opt_levels(args)
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/run_smoke_bench", line 196, in test_opt_levels
    check_added(args, output_file)
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/run_smoke_bench", line 389, in check_added
    doctor.check()
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/Benchmark_Driver", line 734, in check
    self.analyze(self.measure(test))
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/Benchmark_Driver", line 729, in analyze
    rule(benchmark_measurements)
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/Benchmark_Driver", line 630, in _constant_memory_use
    (min_i1, max_i1), (min_i2, max_i2) = [
  File "/Users/ec2-user/jenkins/workspace/swift-PR-macos-perf/swift/benchmark/scripts/Benchmark_Driver", line 631, in <listcomp>
    (min(memory_use), max(memory_use))
TypeError: '<' not supported between instances of 'NoneType' and 'NoneType'

Error is unrelated.