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

ui/build/finder.go

@@ -87,6 +87,8 @@ func NewSourceFinder(ctx Context, config Config) (f *finder.Finder) {
 			"TEST_MAPPING",
 			// Bazel top-level file to mark a directory as a Bazel workspace.
 			"WORKSPACE",
+			// METADATA file of packages
+			"METADATA",
 		},
 		// Bazel Starlark configuration files and all .mk files for product/board configuration.
 		IncludeSuffixes: []string{".bzl", ".mk"},
@@ -189,6 +191,13 @@ func FindSources(ctx Context, config Config, f *finder.Finder) {
 		ctx.Fatalf("Could not find OWNERS: %v", err)
 	}
 
+	// Recursively look for all METADATA files.
+	metadataFiles := f.FindNamedAt(".", "METADATA")
+	err = dumpListToFile(ctx, config, metadataFiles, filepath.Join(dumpDir, "METADATA.list"))
+	if err != nil {
+		ctx.Fatalf("Could not find METADATA: %v", err)
+	}
+
 	// Recursively look for all TEST_MAPPING files.
 	testMappings := f.FindNamedAt(".", "TEST_MAPPING")
 	err = dumpListToFile(ctx, config, testMappings, filepath.Join(dumpDir, "TEST_MAPPING.list"))