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- We may use *CHECK* macros instead of *ASSERT* macros.
- We may use *LOG* macros instead of WTF_LOG.

- Update the following files as examples:
  - HashTable.h
  - RefCountedLeakCounter.cpp
    It uses VLOG(0) because the log channel was enabled by default.
  - StringBuilder.*
  - TextCodecICU.cpp
  - TextEncodingRegistry.cpp

- Move WTFTestPrinters implementation to WTFString.cpp and AtomicString.cpp in
  order to pass String and AtomicString to base/logging macros.
  Also, this CL removes wtf_unittest_helpers build target.

This CL has no behavior changes.

Review URL: https://codereview.chromium.org/1807853003

Cr-Commit-Position: refs/heads/master@{#381919}