Add explicit error codes for an invalid URL to the SDK

[nshestakov]

Now, if you try to connect via the C++ SDK using the wrong URL, you get a TRANSPORT_ERROR, and the error text in Issues is "Misformatted domain name" or "Domain name not found". I would like to clearly distinguish these errors by the error code.

Examples:

"grp§c://localhost:2135"
"grpc://domain-not-exists-localhost.com.moc:2135"

#18943