Getting all annotations to an obsolete term in a single search

[ukemi]

As an add-on or perhaps concurrently with #98, the MGI curators would also like to be able to do a search that returns all annotations to obsolete terms. #98 allows for the search of individual terms, but curators would find it useful to be able to do the more global search to see if they have missed any clean-up. In those cases, they might not know which specific term on which to search.
ping @LiNiMGI

[vanaukenk]

On 2023-05-23 annotation call, @hattrill also requested this feature