Add filter to only show "restricted access" permissions

Problem/Motivation

When a site has a lot of permissions it can be hard to keep track of which ones affect different types of users. This is especially important when some permissions are listed as "restricted access", meaning that site owners need to be sure that only trusted users should have this permission. With potentially hundreds of individual permissions on a site it is difficult to verify which user roles might have a "restricted access" permission.

A separate issue exists to add this to core: #3620382: Add filter on permissions page to only show "restricted access" permissions

Proposed resolution

Add a filter on the permissions page which only shows restricted permissions.

Remaining tasks

Add a filter on the permissions page which only shows restricted permissions.
Test coverage.

User interface changes

A filter is added to the permissions page that results in only permissions showing that have the "restricted access" flag enabled.

Introduced terminology

n/a

API changes

TBD

Data model changes

n/a

Release notes snippet

TBD