Revisit client error when server aborts connection due to MaxConnections (ice protocol)

[bernardnormier]

When an ice-protocol server rejects a new connection because MaxConnections is reached, it aborts the transport connection:

icerpc-csharp/src/IceRpc/Server.cs

Line 908 in c866c08

_transportConnection!.Dispose();

This abort is in turn received by the client as an IceRpcError.ConnectionAborted (fine) or uncategorized error (IceRpcError.IceRpcError). See #2462.

This behavior is problematic because the ConnectionCache "move to the next server address" requires specific error codes, and IceRpcError.IceRpcError (= uncategorized error) is not among them. See #4027.