[compiler-rt][ASan] Fix description of __sanitizer_annotate_contiguous_container

This revision updates the description of
`__sanitizer_annotate_contiguous_container` in includes. Possibilites of
the function were changed in D132522 and it supports:
  - unaligned beginning,
  - shared first/last granule with other objects.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D149341