scudo: Use more size classes in the malloc_free_loop benchmarks.

[pcc]

Summary

As a result of recent changes to the Android size classes, the malloc_free_loop
benchmark started exhausing the 8192 size class at 32768 iterations. To avoid
this problem (and to make the test more realistic), change the benchmark to
use a variety of size classes.

[merge_guards_bot]

Unit tests: pass. 62422 tests passed, 0 failed and 845 were skipped.

clang-tidy: fail. clang-tidy found 1 errors and 0 warnings. 0 of them are added as review comments below (why?).

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

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compiler-rt/lib/scudo/standalone/benchmarks/malloc_benchmark.cpp

std::unique_ptr<AllocatorT, decltype(Deleter)> Allocator(new AllocatorT,
                                                            Deleter);
   Allocator->reset();
 
   const size_t NumIters = State.range(0);
   size_t PageSize = scudo::getPageSizeCached();
   void *Ptrs[NumIters];
 
   for (auto _ : State) {
+    size_t SizeLog2 = 0;
     for (void *&Ptr : Ptrs) {
-      Ptr = Allocator->allocate(8192, scudo::Chunk::Origin::Malloc);
+      Ptr = Allocator->allocate(1 << SizeLog2, scudo::Chunk::Origin::Malloc);
       auto *Data = reinterpret_cast<uint8_t *>(Ptr);
-      for (size_t I = 0; I < 8192; I += PageSize)
+      for (size_t I = 0; I < 1 << SizeLog2; I += PageSize)
         Data[I] = 1;
       benchmark::DoNotOptimize(Ptr);
+      SizeLog2 = (SizeLog2 + 1) % 16;
     }
     for (void *&Ptr : Ptrs)
       Allocator->deallocate(Ptr, scudo::Chunk::Origin::Malloc);
   }
 
   State.SetBytesProcessed(uint64_t(State.iterations()) * uint64_t(NumIters) *
                           8192);
 }