[Linux] Improve network connection implementation

[lemonmojo]

• Maybe add a lightweight abstraction of the POSIX socket APIs so that it's easier and safer to work with
• Proper error handling
• Get rid of the extra errors defined in LinuxNetworkConnection and re-use existing ones or add new ones from ConnectionError or ProtocolError (https://github.com/royalapplications/royalvnc/tree/main/Sources/RoyalVNCKit/SDK/Error)
• Detect and handle connection state changes (maybe with TCP Keep Alive setting?)