xds: revert #8310: migration of xdsclient to use generic client and dedicated LRS client

This reverts commit 996aabe.

Author: arjan-bal

internal/xds/bootstrap/bootstrap.go

@@ -217,16 +217,10 @@ func (sc *ServerConfig) ServerFeaturesIgnoreResourceDeletion() bool {
 	return false
 }
 
-// SelectedCreds returns the selected credentials configuration for
-// communicating with this server.
-func (sc *ServerConfig) SelectedCreds() ChannelCreds {
-	return sc.selectedCreds
-}
-
 // DialOptions returns a slice of all the configured dial options for this
-// server except grpc.WithCredentialsBundle().
+// server.
 func (sc *ServerConfig) DialOptions() []grpc.DialOption {
-	var dopts []grpc.DialOption
+	dopts := []grpc.DialOption{sc.credsDialOption}
 	if sc.extraDialOptions != nil {
 		dopts = append(dopts, sc.extraDialOptions...)
 	}