tsan: make all memory mappings testable

Currently we define/compile the mapping for a platform
only on that platform. This makes it impossible to unit-test
them on a single platform, and even to build test.
We have 17 of them and the Go mappings will be tested
only after a manual episodic update of the Go runtime.

Define all mappings always with unique names.
This will allow to unit-test them.
No functional changes.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D107734