jobs endpoint - high cpu / memory query

[ITJamie]

Describe the bug
the jobs/filter endpoint gets loaded when viewing the jobs page. the user_list query is unoptimised
When you have a jid's table with a few 100k rows it can bring your machine to a crawl.
the current code has to load every single row into memory. json parse it in python then find all unique "users" across every dict.
while this is fine in a dev environment, it can consume gigs of memory on a large db.

To Reproduce
create or import a very large jid's table.
load the jobs page in alcali a few times. watch memory usage on postgres + python alcali gunicorn

Expected behavior
not consuming multiple gb of memory

Additional context
I would recommend removing the user_list filter on this endpoint OR at least giving a config option to disable it.
The jid's table does not have a username column to filter on by default, any searching of it is going to cpu and memory intensive on larger dbs