Pinned Filters

[yoshnopa]

As Proposed in #3549, this Pull Provides the possibility to pin filters to the top of the Filter list.
That way, more commonly used filters are available more quickly without compromising on the wide range of possible filter options.
In the backend, this works very similar to the savedfilter, just without the actual filter and the messageid of the filter as the "name".
In the frontend, the only directly visible change is a pin on the right side of the filters:

Clicking on the pin will put the according option to the top, separated by a divider:

Of course, the pinned options are saved per media type, so you can have different pinned filters in the scene section than in the tag section.

Closes #3549

[kermieisinthehouse]

Thank you for contributing to Stash! This is a great change.

Functionality tested; working.
Code reviewed.

My only note is to not lay it out with a right: 15%, but instead to make the whole row a flexbox, and make the caption flex-grow to take up the entire middle. That way, we don't have weird layout and the button position is determined by the padding of the parent row.

[yoshnopa]

Thanks @DingDongSoLong4 for the Code Revision and additions!
Just for documentation, the following was changed:

• Divider is now just empty space, as we don't use such a thing elsewhere
• On hover, the pin rotates, giving a visual cue for the user
• The x and pin swapped places, it looks fancier. I'm open for debate on that one
• Flex is used for positioning. Generally the Code has been polished from my "let's try some react!"-state

Also thank you @kermieisinthehouse for looking into it!

[kermieisinthehouse]

Code reviewed and tested.