Add support for Rust C libraries.

Adds the ability for rust modules to be compiled as C libraries, and
allows cc modules to depend on these rust-generated modules. This also
means that soong-rust should not have any dependencies on soong-cc aside
from what's required for testing.

There's a couple small fixes included as well:

 - A bug in libNameFromFilePath that caused issues when library's had
 "lib" in their name.
 - VariantName is removed from rust library MutatedProperties since this
 was unused.

Bug: 140726209
Test: Soong tests pass.
Test: Example cc_binary can include a rust shared library as a dep.
Test: m crosvm.experimental
Change-Id: Ia7deed1345d2423001089014cc65ce7934123da4

cc/fuzz.go

@@ -207,7 +207,7 @@ func (s *fuzzPackager) GenerateBuildActions(ctx android.SingletonContext) {
 
 		// Discard vendor-NDK-linked modules, they're duplicates of fuzz targets
 		// we're going to package anyway.
-		if ccModule.useVndk() || !ccModule.Enabled() {
+		if ccModule.UseVndk() || !ccModule.Enabled() {
 			return
 		}