Discourage use of "Quick query" in single-folder workspaces

[shati-patel]

The "Quick query" command creates a new workspace folder, which doesn't work well for users in single-folder workspaces. This PR adds a prompt for those people to encourage them to use the new "Create query" command instead:

See internal linked issue for more details.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.
  • N/A: No docs change needed

[charisk]

Looking good in general, just a quick question around the new command.