Add UI options tab and setting to disable opening diff in a new tab

[OPerepadia]

Following the discussion in #2839, I've added a UI options tab in settings with an option to prevent the diff page from opening in a new tab.
I've tested it and everything seems to work as expected. Please let me know if any changes are needed to merge this.

[dgtlmoon]

better is if you can move it to something like

{{ render_checkbox_field(form.application.form.ui.from.open_diff_in_new_tab, class="open_diff_in_new_tab") }}

it needs to be in its own "UI" dict because in the future there will likely be a lot more options

[dgtlmoon]

also needs sub form added

[OPerepadia]

Done

[dgtlmoon]

the PR breaks all tests at the linting stage for some reason hmm

[dgtlmoon]

#3074

[dgtlmoon]

alright, now rebase or merge out master your way :) and repush

[dgtlmoon]

Ok and now you need to add a test, its enough to copy some test from tests/test_... and call it test_ui.py , its enough for the test to turn on/off the checkbox and see its reflected in the template output/ get overview page

[OPerepadia]

It's strange, one of the checks failed with python 3.10. I'm not sure if the issue is with my test, because it passed according to the logs, but this one failed: tests/visualselector/test_fetch_data.py::test_setup

[dgtlmoon]

it can be intermittant, i'll run that one again

[dgtlmoon]

thanks!