Refactor CC to prep for Rust sanitizable modules.

Adds a PlatformSanitizable interface which both CC and Rust can
implement so that the sanitizer mutators in CC can sanitize Rust
shared/static libraries appropriately.

Bug: 147140513
Test: m nothing
Change-Id: Ib31103b6c4902a4d5df2565c0d7c981298d100a3