[Sanitizers] Make common allocator agnostic to failure handling modes.

Summary:
Make common allocator agnostic to failure handling modes and move the
decision up to the particular sanitizer's allocator, where the context
is available (call stack, parameters, return nullptr/crash mode etc.)

It simplifies the common allocator and allows the particular sanitizer's
allocator to generate more specific and detailed error reports (which
will be implemented later).

The behavior is largely the same, except one case, the violation of the
common allocator's check for "size + alignment" overflow is now reportied
as OOM instead of "bad request". It feels like a worthy tradeoff and
"size + alignment" is huge in this case anyway (thus, can be interpreted
as not enough memory to satisfy the request). There's also a Report()
statement added there.

Reviewers: eugenis

Subscribers: kubamracek, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D42198

llvm-svn: 322784