Enhancement: Purging multiple histories through the UI is slow and often ends in "grid failure"

This is not new yet has been brought up by users recently.

I personally have had this issue for at least several releases/years.

Reloading the page will resolve, but perhaps we can be better (tune the processing).

Bonus1: Currently, the user is stuck in the Saved Histories view during processing. An alternative: mark histories for purging (as usual) then process in the background. When done, give the user a pop-up or some other status cues in UI that this is "done" without issues or failures in the sub-jobs (confirmation info, could even list out history names/sizes). If any were skipped (perhaps were still shared), include that in confirmation and tell the user to unshare and try again (not to send in a bug report).

Bonus2: An override option to purge histories regardless of share status similar to `rm -rf`.

Start by reproducing the Saved Histories UI flow while purging multiple histories and observe when processing becomes slow or shows "grid failure." The issue names no files, tests, or entry points; done would require a decided approach for processing, completion or failure status, and the proposed shared-history behavior.

Written by the indexing model from the issue text.