Move stubs related methods out of LinkableInterface

The stubs methods are very specific to cc for now, move them out
of LinkableInterface so they are not shared with rust.  Instead,
create a cc.Module.library field that contains the libraryInterface
to simplify calling libraryInterface methods on cc modules.

Test: all Soong tests
Test: no change to Soong outputs
Change-Id: I0289d866ce1f7a765631fe3101a62b1b4988ba1c
diff --git a/cc/toolchain_library.go b/cc/toolchain_library.go
index 8c546c5..0c934ad 100644
--- a/cc/toolchain_library.go
+++ b/cc/toolchain_library.go
@@ -66,6 +66,7 @@
 	module.stl = nil
 	module.sanitize = nil
 	module.installer = nil
+	module.library = toolchainLibrary
 	module.Properties.Sdk_version = StringPtr("current")
 	return module.Init()
 }