Depends on https://github.com/orgs/coder/projects/41/views/1?pane=issue&itemId=94820346

When a devcontainer is specified, the agent should watch for changes to those files and publish an event on the workspace updates channel (e.g. agt_devcontainer_files_updated) to notify consumers that the files relating to the devcontainer were modified.

Only notify the files were modified since the devcontainer was started.
We should debounce these notifications as well.

For now, only support this on agents running on Linux platforms.