Added support for immortal streams to maintain persistent TCP connections to workspace services that automatically reconnect when interrupted.

What changed?

• Implemented a new immortal streams feature that provides persistent TCP connections to workspace services
• Created CLI commands for managing immortal streams (coder exp immortal-stream list/delete)
• Added support for using immortal streams with SSH and port forwarding connections
• Implemented server-side API endpoints for creating, listing, and deleting immortal streams
• Added fallback mechanism to regular connections when immortal streams are unavailable

How to test?

1. Use the experimental CLI commands to manage immortal streams:

   coder exp immortal-stream list <workspace-name>
   coder exp immortal-stream delete <workspace-name> <stream-name>
   

2. Test SSH with immortal streams:

   coder ssh --immortal <workspace-name>
   

3. Test port forwarding with immortal streams:

   coder port-forward --immortal <workspace-name> <local-port>:<remote-port>
   

4. Verify automatic reconnection by temporarily disrupting the network connection

Why make this change?

Immortal streams provide a more resilient connection mechanism for workspace services, automatically reconnecting when network interruptions occur. This improves the user experience by maintaining persistent connections to SSH and port-forwarded services, reducing the need for manual reconnection and preventing session loss during temporary network issues.