Add Code Metadata rule to soong/testing.

This Cl adds a new rule to Soong to generate code ownership metadata. Also, this CL adds a provider in the Java SDK library to provide generated source files to the Code_metadata rule. Will add providers to other libraries in the future changes.

Bug: 296873595
Change-Id: Ic2e43aa9b161231fea4416d1f0d36b778361d7c5
diff --git a/testing/code_metadata_internal_proto/OWNERS b/testing/code_metadata_internal_proto/OWNERS
new file mode 100644
index 0000000..03bcdf1
--- /dev/null
+++ b/testing/code_metadata_internal_proto/OWNERS
@@ -0,0 +1,4 @@
+dariofreni@google.com
+joeo@google.com
+ronish@google.com
+caditya@google.com