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.

[pepone]

We currently have:

SocketError	IceRpcError
AddressAlreadyInUse (10048)	AddressInUse
ConnectionAborted (10053)	ConnectionAborted
ConnectionReset (10054)	ConnectionAborted
HostUnreachable (10065)	ServerUnreachable
NetworkUnreachable (10051)	ServerUnreachable
Shutdown (10058)	ConnectionAborted
ConnectionRefused (10061)	ConnectionRefused
OperationAborted (995)	OperationAborted

icerpc-csharp/src/IceRpc/Transports/SocketExceptionExtensions.cs

Lines 19 to 33 in e672eaf

	IceRpcError errorCode = exception.SocketErrorCode switch
	{
	SocketError.AddressAlreadyInUse => IceRpcError.AddressInUse,
	SocketError.ConnectionAborted => IceRpcError.ConnectionAborted,
	// Shutdown matches EPIPE and ConnectionReset matches ECONNRESET. Both are the result of the peer closing
	// non-gracefully the connection. EPIPE is returned if the socket is closed and the send buffer is empty
	// while ECONNRESET is returned if the send buffer is not empty.
	SocketError.ConnectionReset => IceRpcError.ConnectionAborted,
	SocketError.HostUnreachable => IceRpcError.ServerUnreachable,
	SocketError.NetworkUnreachable => IceRpcError.ServerUnreachable,
	SocketError.Shutdown => IceRpcError.ConnectionAborted,
	SocketError.ConnectionRefused => IceRpcError.ConnectionRefused,
	SocketError.OperationAborted => IceRpcError.OperationAborted,
	_ => IceRpcError.IceRpcError
	};

I think the core issues is that many error codes are just handled as a generic IceRpcError

https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.socketerror?view=net-10.0

Seems we can improve the mapping above