Use manifest merger in Soong

Move the manifest merger config to Soong, and use it to merge
manifests of static dependencies of android_library and android_app
modules.

Bug: 110848854
Test: m checkbuild
Change-Id: Ib89e1f1a52a8b76157e4e0348baf42800412df0d

java/app.go

@@ -72,6 +72,10 @@ func (a *AndroidApp) ExportedStaticPackages() android.Paths {
 	return nil
 }
 
+func (a *AndroidApp) ExportedManifest() android.Path {
+	return a.manifestPath
+}
+
 var _ AndroidLibraryDependency = (*AndroidApp)(nil)
 
 type certificate struct {