[UX] Add Filter Permissions module to core

Description of the need

The permissions page is a bit of a mess in terms of UI, too many options make it very difficult to find specific permissions. We have a general ticket about improving the UI of the permissions page, this specific ticket is for anyone who wants to advocate for this specific solution.

I haven't looked at all the options, but I've looked at the recently ported "Filter Permissions" module and feel like it's a pretty simple module that would be a huge improvement.

I would assume that this kind of improvement could be made better later if people have other ideas. But, integrating this module into core could be a quick and easy UI win.

Proposed solution

Add Filter Permissions module to core.

Alternatives that have been considered

See: * https://github.com/backdrop/backdrop-issues/issues/463 * https://github.com/backdrop/backdrop-issues/issues/980

Personally, I'm open to other options. But, this one seems really good and would be pretty quick and easy to implement (I believe).

Draft of feature description for Press Release (1 paragraph at most)

We've included the Filter Permissions module into core which is a dramatic improvement in the user interface for Backdrop CMS. The Filter Permissions module adds a Role and Module based filter to the top of the permissions page which helps a site administrator quickly find the particular permission that they are looking for.