[ASan] Remove sanity checks during annotation of contiguous container

[ASan] Remove sanity checks during annotation of contiguous container

This revision removes sanity checks in
`__sanitizer_annotate_contiguous_container`.
(Changed them to `DCHECK_EQ`.)
Those checks may be problematic, if someone manually unpoisoned memory block.
Manual unpoisoning may be used if part of the program is not
instrumented.

Those checks are helpful while confirming correctness of ASan annotations
implementation.

Originally suggested here: https://reviews.llvm.org/D136765#4174546

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D145482