This is spun off from bug#52237[1]. There's a minor issue with 
`context-menu-mode' where some of the separators are named 
`FOO-separator' and others are named `separator-FOO'. Since these 
separators are partially useful for context menu functions to find the 
right place to insert their items, this inconsistency could be pretty 
confusing for authors of those functions (e.g. in third-party packages).

This patch renames the separators to `FOO-separator' following the logic 
in the above-linked comment (in short, `FOO' is a noun adjunct modifying 
the actual object: a separator). To verify that I changed all the 
appropriate places and didn't miss anything, I ran the following command 
and manually looked over all the results to eliminate false positives:

   ag '(?<![\w-])separator-+[A-Za-z][\w-]*' ../lisp -G '.*\.el$'

I've tested the patch on both Emacs 28 and 29 and don't see any issues 
in either.

Hopefully this is a small enough change to make it into Emacs 28, since 
otherwise I think we'd just have to live with the names as they are 
forever. It wouldn't be very nice to change these names after third 
parties had come to rely on them in Emacs 28, after all.

[1] https://lists.gnu.org/archive/html/bug-gnu-emacs/2021-12/msg00312.html