language_models: Allow overriding Zed completions URL via environment variable (#28323)

This PR adds support for overriding the Zed completions URL via the
`ZED_COMPLETIONS_URL` environment variable.

Release Notes:

- N/A
61b7a05792Marshall Bowers committed on 4/8/2025, 2:46:15 PM· committed by GitHubparentcc15598
1 file changedLine totals unavailable