#7552669 Sidebar: Limit Site Switcher results to 50, including hidden sites

Proposed Changes

Fixes #68043. Fixes #67581. I decided to fix the latter issue in the same PR so we don’t end up in an intermediary state where all hidden sites are shown, despite having no way to limit the results.

Testing Instructions

Considering you have more than 50 sites:

1. See that there is a 50 result limit, including some hidden sites, in the site switcher in the sidebar;
2. Type a single letter in the search box and check that even the filtered results are limited to 50.

If you don’t, modify the value of maxResults to assert that the instructions hold true.