[hwasan] add stack frame descriptions.

Summary:
At compile-time, create an array of {PC,HumanReadableStackFrameDescription}
for every function that has an instrumented frame, and pass this array
to the run-time at the module-init time.
Similar to how we handle pc-table in SanitizerCoverage.
The run-time is dummy, will add the actual logic in later commits.

Reviewers: morehouse, eugenis

Reviewed By: eugenis

Subscribers: srhines, llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D53227

llvm-svn: 344985