feat(plg): require confirmation before removing user or revoking admin

[taras-yemets]

Closes #63240

Adds a confirmation modal before revoking admin or removing user.

Test plan

• Run Sourcegraph instance in dotcom mode
  • Sign in as Cody Pro team site admin
  • Navigate to "/cody/team/manage" page
  • Click on remove button next to the team member
    • Ensure the confirmation modal is visible
    • Ensure clicking the cancel button closes the confirmation modal and user is not removed
    • Ensure clicking the confirm button removes the user and closes the confirmation modal
  • Click on the revoke admin button next to the team admin
    • Repeat steps for the user removal

Changelog

[taras-yemets]

@rrhyne, I've just watched your Loom and now working on updating this PR accordingly (confirmation text messages, alert and button styles, etc.)

[vdavid]

Good enough for me, and if something is off, we can iterate from here.