[SSAF][UnsafeBufferUsage] Make UnsafeBufferUsageExtractor a registered ASTConsumer (#191931)
- Removed UnsafeBufferUsageExtractor.h
- Registered UnsafeBufferUsageExtractor
- Changed unit tests to enable the extractor with
`HandleTranslationUnit`
- Fixed bugs in `UnsafeBufferUsageExtractor::HandleTranslationUnit`
---------
Co-authored-by: Balázs Benics <benicsbalazs@gmail.com>