Add gcov coverage support to Rust modules.

This adds gcov coverage support for Rust device library and binary
modules (including test modules). Support is provided to pass Rust
static library gcno files to CC modules and visa versa.

Additional changes:
 * Begin mutator added for Rust modules.
 * SuffixInList added to android package.
 * CoverageEnabled added to Coverage interface.
 * CoverageFiles added to LinkableLibrary interface.
 * Fix in coverage mutator for non-CC modules which marked the wrong
   variant as the coverage variant.
 * Added coverage libraries to the cc.GatherRequiredDepsForTest.

Bug: 146448203
Test: NATIVE_COVERAGE=true COVERAGE_PATHS='*' m -j <rust_module>
Change-Id: If20728bdde42a1dd544a35a40f0d981b80a5835f