Prevent workspaces from being kept alive when they should not

[stirby]

Functional duplicate of coder/vscode-coder#309 for the Jetbrains extension.

When users stop their workspaces in the dashboard, an idle jetbrains gateway session may reconnect them, and start the workspace when the user is not present. This can incur unnecessary costs for administrators while devs are not active.

We should copy the behavior Asher describes here if possible.

Is there a workspace build going on? If so, wait for that build.
Is the workspace on? If not, prompt to start the workspace and depending on the response go back to 1 or quit.
Otherwise wait for the agent to be ready then connect, or exit if the agent enters some failed/off state.

[Kira-Pilot]

We can do this in Gateway but not in the IDE. Would be nice to explore ways to give this notification priority as Gateway will often be running in the background - maybe with a highlight or by having Gateway pop up as the active window or something.

[Kira-Pilot]

@stirby removing the P2 label basis our slack convo; please add it back if I'm incorrect in doing so.