For #109277

- Add `option` opener priority. This means the oper will only be shown if requested but will not replace the default opener
- Persist registered openers for IntelliSense suggestions

Reworking external opener implementation to allow configured openers to be called directly without a canOpen check

If the user has configured a specific external uri opener, we should always try to use that without first calling `canOpen` to filter down the list of openers.

This change also adds `ExternalUriOpenerEnablement` which allows an opener to mark itself as the preferred opener for a given uri. If only a single preferred opener is returned, it will be used automatically for that uri (although user configuration can override this)

For #109277

- Add more explicit two phase structure to api
- Make opener pass along label when registered

This workbench service handles opening external uris. Unlike the core OpenerService, it also has logic for configuring a default opener and prompting if multiple openers are availble for a given uri