[Task]: Show workspaces currently using provider

[danbarr]

Description

When you delete a provider, there may have been workspaces using it. Their model selection gets removed, but it's not clear which workspaces were impacted.

It would be nice to see a list of workspaces using a provider, both on the providers list and when confirming deletion of a provider (with a message like "The following workspaces are using this provider and will lose their selected model").

Additional Context

No response

[peppescg]

That makes sense to me, but I can also do it with the current endpoint but I would prefer to have a dedicated endpoint for doing it.
cc @jtenniswood a confirmation modal like for delete workspace I think is good enough

[peppescg]

I would split this into two steps, the first one showing the workspaces impacted within the provider deletion.
I created this example, I think it could be good enough:

The second step is to refactor/replace the table showing the list of models and workspaces by provider, but I need to work with James on this, cause the impact is quite different.

@danbarr what is your feedback about this plan?

[danbarr]

@peppescg looks good, I might just suggest a wording update to give the user a next step, like:
"The following workspaces are currently using this provider and will need to be updated:"