Refactor search page and sort pickers

[hjiangsu]

Pull Request Description

This PR refactors the search page logic and fixes a few issues:

• Added new search sort types enum to use for search related queries. These now match up with web UI's options.
• Refactored existing post/comment sort pickers into a single widget (works with post/comment/search sort types)
• Refactored the search page and related widgets into smaller widgets, which should help with readability and maintainability

With this refactor, I've also cleaned up the search filters to remove filters that don't generally make sense.

• Creator and community filters are only shown to post/comment search types. These filters don't currently work with community/user search types.
• Creator filter is hidden for PieFed instances as that's not an available option with their API at the moment

Issue Being Fixed

Issue Number: #1951, #1049

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?