[hwasan] do not check if freed pointer belonged to allocator.

[hwasan] do not check if freed pointer belonged to allocator.

In that case it is very likely that there will be a tag mismatch anyway.

We handle the case that the pointer belongs to neither of the allocators
by getting a nullptr from allocator.GetBlockBegin.

Reviewed By: hctim, eugenis

Differential Revision: https://reviews.llvm.org/D108383