[msan] Add static to some msan allocator functions

This is to help review refactor the allocator code.
So it is easy to see which are the real public interfaces.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D101586

GitOrigin-RevId: c027272ac260785849ae8afbb26742d5b7499ae5
1 file changed