Refactor and overhaul instance discovery page

[hjiangsu]

Pull Request Description

This PR refactors and overhauls the instance page. At a high level, the following changes were made:

• Fixed an issue where a remote instance page was displaying local instance information
• Improved the logic for loading/fetching instance contents (posts, comments, users, communities)
• Improved logic for handling instance item resolution to local instance
• Added the ability to search instance and apply different sorts for results
• Fixed an issue where user resolution was failing due to incorrect API parsing

This is a fairly large change so some issues may come up! I've done some general testing on my end to ensure the general flows work as expected.

Issue Being Fixed

Issue Number: #503, #2015

Screenshots / Recordings

Checklist

• If a new package was added, did you ensure it uses an appropriate license and is actively maintained?
• Did you use localized strings (and added appropriate descriptions) where applicable?
• Did you add semanticLabels where applicable for accessibility?