Rename generate proto config file to match classpath type.

There is no need to leak soong module names.

Bug: 180105615
Test: m && launch_cvd; atest CtsClasspathsTestCases
Change-Id: I04f4e181d2f42b9d71641980a2c7c4e8cbc8e426
diff --git a/java/classpath_fragment.go b/java/classpath_fragment.go
index bc0416a..0e14d24 100644
--- a/java/classpath_fragment.go
+++ b/java/classpath_fragment.go
@@ -105,7 +105,7 @@
 }
 
 func (c *ClasspathFragmentBase) generateClasspathProtoBuildActions(ctx android.ModuleContext, jars []classpathJar) {
-	outputFilename := ctx.ModuleName() + ".pb"
+	outputFilename := strings.ToLower(c.classpathType.String()) + ".pb"
 	c.outputFilepath = android.PathForModuleOut(ctx, outputFilename).OutputPath
 	c.installDirPath = android.PathForModuleInstall(ctx, "etc", "classpaths")