Allow for explicit bind address in `servenv`

This is a follow-up issue of https://github.com/vitessio/vitess/pull/12987 that should be carried on in v18.

From #12987:
> By moving everything away from the default mux to an explicit mux for the servenv, we can make this configurable in the near future.
> The changes here now explicitly add the profiling endpoints so that we can make that optional in a follow up.