Add "force-read-only" mode to xx_aconfig_library build rules

Test: added unit tests and CI
Bug: 317115655
Change-Id: Ia72159ffe072f9b4997f0d4d55a7b3db5356f5ed
diff --git a/aconfig/codegen/rust_aconfig_library.go b/aconfig/codegen/rust_aconfig_library.go
index 73b6fec..2ab54b6 100644
--- a/aconfig/codegen/rust_aconfig_library.go
+++ b/aconfig/codegen/rust_aconfig_library.go
@@ -23,6 +23,7 @@
 	// default mode is "production", the other accepted modes are:
 	// "test": to generate test mode version of the library
 	// "exported": to generate exported mode version of the library
+	// "force-read-only": to generate force-read-only mode version of the library
 	// an error will be thrown if the mode is not supported
 	Mode *string
 }