bp2build: add converted modules to codegen metrics, and remove the
compat layer.

The list of converted modules is used for tracking bp2build progress.

The module_name_to_label aliases weren't really adding much value to
mixed builds, so let's drop the feature for now and simplify the code.

Test: CI
Test: USE_BAZEL_ANALYSIS=1 m droid
Change-Id: I3269344cfe6d1c72c108d66c6e820bc0ec19bb34
diff --git a/bp2build/conversion.go b/bp2build/conversion.go
index 75bc2b4..354abf6 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -16,29 +16,19 @@
 	Contents string
 }
 
-func CreateSoongInjectionFiles(compatLayer CodegenCompatLayer) []BazelFile {
+func CreateSoongInjectionFiles(metrics CodegenMetrics) []BazelFile {
 	var files []BazelFile
 
 	files = append(files, newFile("cc_toolchain", GeneratedBuildFileName, "")) // Creates a //cc_toolchain package.
 	files = append(files, newFile("cc_toolchain", "constants.bzl", config.BazelCcToolchainVars()))
 
-	files = append(files, newFile("module_name_to_label", GeneratedBuildFileName, nameToLabelAliases(compatLayer.NameToLabelMap)))
+	files = append(files, newFile("metrics", "converted_modules.txt", strings.Join(metrics.convertedModules, "\n")))
 
 	return files
 }
 
-func nameToLabelAliases(nameToLabelMap map[string]string) string {
-	ret := make([]string, len(nameToLabelMap))
-
-	for k, v := range nameToLabelMap {
-		// v is the fully qualified label rooted at '//'
-		ret = append(ret, fmt.Sprintf(
-			`alias(
-    name = "%s",
-    actual = "@%s",
-)`, k, v))
-	}
-	return strings.Join(ret, "\n\n")
+func convertedModules(convertedModules []string) string {
+	return strings.Join(convertedModules, "\n")
 }
 
 func CreateBazelFiles(