xds: check type_url field of typed_config for extensions instead of the legacy name field

[easwars]

Currently, there are two extensions that we need to care about:

• the TransportSocket extension where we check for name field to be envoy.transport_sockets.tls, and
• the custom cluster type extension where we check for name field to be envoy.clusters.aggregate

In both these cases we need to instead check the type_url field inside of the typed_config.

See related C-core change for the same grpc/grpc#31024

[easwars]

There could be more, we probably need to do an audit and check for pretty much any Any field. Another way to scan for it is any protobuf that we use whose name starts with envoy.extensions.