Add an internal API to validate a target URI #8747
Description
There are many places (most notably in the xDS codebase) where we receive configuration that contains the target URI of a gRPC service that we need to talk to. It would be nice to have an internal API that validates these target URI strings:
- the target URI must parse as a valid RFC 3986 string
- the scheme specified in the URI must have a name resolver registered with gRPC