Clean up member-less teams

[gtsiolis]

Bug description

While we now delete teams from the database when a user deletes a team (see #6273) we still have not resolved what happens to teams when the last team owner member tries to leave the team (see #4623).

This causes some confusion as users can not reuse a team name after leaving a team as the last team member, see #6273 (comment).

Some of these teams also surface on the team scope selector.

We should probably resolve #4623 first and then clean up the the database and remove member-less teams. 🗺️

Steps to reproduce

1. Create a team
2. Go to team members
3. Leave the team
4. Try creating a new team with the same name

Workspace affected

No response

Expected behavior

No response

Example repository

No response

Anything else?

No response

[jldec]

/schedule

[roboquat]

@jldec: Issue scheduled in the meta team (WIP: 0)

In response to this:

/schedule

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