[GWP-ASan] Minor refactor of optional components.

Authored by hctim on Jan 13 2021, 5:28 PM.


[GWP-ASan] Minor refactor of optional components.

In preparation for the inbuilt options parser, this is a minor refactor
of optional components including:

  • Putting certain optional elements in the right header files, according to their function and their dependencies.
  • Cleaning up some old and mostly-dead code.
  • Moving some functions into anonymous namespaces to prevent symbol export.

Reviewed By: cryptoad, eugenis

Differential Revision: https://reviews.llvm.org/D94117