Rework code shim

[felipecrs]

Highlights:

• Fix opening remote ssh sessions since vscode changed ~/.vscode-server/bin to ~/.vscode-server/cli
• Add support for --devcontainer on remote ssh and remote tunnel
• Rename USE_NATIVE_CODE env var to NO_REMOTE
• Fix cases where NO_REMOTE would not prevent use of remote sessions, like when ran from inside a vscode terminal
• Avoid pruning non-working sockets to avoid messing with vscode (they should clean up them, not us)
• Several other minor fixes and improvements
• Better logging
• Better error handling