[Tagging] Enable or Disable Taxonomies from the UI

[bradenmacdonald]

"As a global staff user (aka 'instance-level super-user'), I can enable or disable taxonomies."

Depends on #104 , relates to and should follow #105

Acceptance criteria

1. If and only if the user has permission to enable/disable taxonomies (they are global staff), display this new gear icon on each Taxonomy card:
   
2. Clicking it should show this menu:
   
3. System-defined taxonomies cannot be enabled/disabled, so this menu won't appear for them.
4. Clicking "Disabled" or "Enabled" should call the API, make that change, and update the view to reflect the new status of the taxonomy, along with showing this toast at the bottom of the page:
   .
   
5. If clicking the menu option to disable a Taxonomy, this prompt will first appear to confirm the action:
   

Developer notes

• Don't check if the user is global staff - check if they have "enable/disable permission" for the given taxonomy, and there should be a rule that only global staff have that permission, and only if the taxonomy is not system-defined.
• Screenshots above are for convenience - Figma is the most up-to-date source for mockups. The scale of UI elements seen in the screenshots above may be incorrect.
• Definitions for future reference: "Enabled: Course authors are able to add tags from the taxonomy to content in their courses and libraries. Disabled: Course authors are not able add tags from the taxonomy to content in their courses and libraries. Authors will not even see the taxonomy at the course level if it is disabled. If a taxonomy is disabled and it has tags in use, then the tags would disappear from the course view. However, the association of the content to the tags would remain intact, so that if the taxonomy is enabled again later, authors would not have to re-tag their content."