Add llndk_stubs property

Prepare for making the relationship between an llndk_library stubs
module and the cc_library implementation module explicit by
adding an llndk_stubs property.  Each cc_library will be updated
to point to its llndk_library, and the llndk_library name will
be changed to make the .llndk suffix explicit.  Then the implicit
connection and suffix can be removed.

Bug: 170784825
Test: m checkbuild
Change-Id: I6b0482a3f286ec29b2e928551aa4317749f2b499

cc/ndk_library.go

@@ -100,10 +100,16 @@ type stubDecorator struct {
 	unversionedUntil android.ApiLevel
 }
 
+var _ versionedInterface = (*stubDecorator)(nil)
+
 func shouldUseVersionScript(ctx BaseModuleContext, stub *stubDecorator) bool {
 	return stub.apiLevel.GreaterThanOrEqualTo(stub.unversionedUntil)
 }
 
+func (stub *stubDecorator) implementationModuleName(name string) string {
+	return strings.TrimSuffix(name, ndkLibrarySuffix)
+}
+
 func ndkLibraryVersions(ctx android.BaseMutatorContext, from android.ApiLevel) []string {
 	var versions []android.ApiLevel
 	versionStrs := []string{}