Revert "Add CopilotRelated command (#59963)"

[Nathan Shively-Sanders (sandersn)]

This reverts commit 52c59db.
This feature didn't help, but it took a long time to verify that.

[TypeScript Bot (typescript-bot)]

Thanks for the PR! It looks like you've changed the TSServer protocol in some way. Please ensure that any changes here don't break consumers of the current TSServer API. For some extra review, we'll ping Sheetal Nandi (@sheetalkamat), Matt Bierner (@mjbvz), Kat Marchán (@zkat), and Joaquin Jares (@joj) for you. Feel free to loop in other consumers/maintainers if necessary.

[TypeScript Bot (typescript-bot)]

Looks like you're introducing a change to the public API surface area. If this includes breaking changes, please document them on our wiki's API Breaking Changes page.

Also, please make sure Daniel Rosenwasser (@DanielRosenwasser) and Ryan Cavanaugh (@RyanCavanaugh) are aware of the changes, just as a heads up.

[Nathan Shively-Sanders (sandersn)]

Ryan Cavanaugh (@RyanCavanaugh) both Daniel Rosenwasser (@DanielRosenwasser) and Sheetal Nandi (@sheetalkamat) are out right now, so I want to make sure you know about this.
It'll need a cherry-pick to 5.7-rc as well.

[Jake Bailey (jakebailey)]

Do all clients understand not to attempt to call this anymore, given the message is removed? I know VS Code traditionally uses version numbers, but this is the first case where something is removed I think, so thinking of people who haven't updated their editors (or the current stable) maybe

[Nathan Shively-Sanders (sandersn)]

Do all clients understand not to attempt to call this anymore, given the message is removed?

No. I thought I had some additional check for the existence of copilotRelated, but I just wrote the usual version check. So I think your offline suggestion of turning this into an empty-array-returning stub until 5.8 is a good one. That way vscode 1.95 won't crash on 5.7.

Actually, it's probably easier to write that from current main instead of on top of a revert, so I'll close this PR and open a new one.

[Nathan Shively-Sanders (sandersn)]

Superceded by #60488