WebUI improvements and gitea tools fix

* The "CA Certificate Bundle (Optional)" showed no indication of a
  certificate being selected. This change fixes that.
* The gitea tools cache worker should not fall back to the default releases
  page if the custom page set by the user returned an error.
* Selecting "Use Internal Tools Metadata" in the gitea endpoint edit modal
  now greys out the "Tools Metadata URL (optional)" text field.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Author: gabriel-samfira