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_proto/regen.sh b/testing/code_metadata_proto/regen.sh
new file mode 100644
index 0000000..ffe06f7
--- /dev/null
+++ b/testing/code_metadata_proto/regen.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+aprotoc --go_out=paths=source_relative:. code_metadata.proto