Change bp2build converter of module "package".

1) Use attribute name "default_package_metadata" instead of
   "default_applicable_licenses" in packages to better describe its use.
2) Add a filegroup "default_metadata_file" in packages to search for
   METADATA file in each package.
3) Include "default_metadata_file" in each package's
   "default_package_metadata" attribute.

Bug: 275472038
Test: CIs
Change-Id: I645c013c39e3190fd96c4a549d39a331aced16bd
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 563199b..18bf3b9 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -400,6 +400,8 @@
 			pbi.Inputs = append(pbi.Inputs,
 				config.Bp2BuildFilesMarkerFile(),
 				filepath.Join(config.FileListDir(), "bazel.list"))
+		case bp2buildFilesTag:
+			pbi.Inputs = append(pbi.Inputs, filepath.Join(config.FileListDir(), "METADATA.list"))
 		}
 		invocations = append(invocations, pbi)
 	}