Add idle timeout

[andrewbaldwin44]

Fixes #1636
References #7177

Proposal

• Add an --idle-timeout-seconds argument that can be used to exit code server when idle
• Add validation to ensure idle timeout is a valid number and that the number is above 60 seconds
• Add a simple unit test case

[code-asher]

Awesome, thank you for tackling this!

[code-asher]

Stellar thank you! Only one thing, looks like the VS Code submodule was updated, probably just accidentally committed, so we need to remove that.

[andrewbaldwin44]

Yup sorry that was added accidentally, should be good now!

[code-asher]

Thank you again!