Optimise MAL search queries by ~11x (#2832)

Previously, the app made one request for the search, and then fired
off 1 request per search result to obtain additional data, such as
each title's synopsis, etc.

However, MAL's search allows field selection during the initial query,
which will return all the data in that first response, avoiding the
massive bunch of requests (and alleviating some pressure on MAL from
our userbase).

By combining the selected fields into one constant, I was able to also
get rid of the MALUserListSearch entirely because it was redundant.
This allows for a unified MALManga->TrackSearch helper, further
reducing complexity.

I got to my "11x" improvement because on page of search results has 10
elements, and this change turns 11 (1+10 for results) requests into 1.

CHANGELOG.md

@@ -16,6 +16,7 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 
 ### Improved
 - Minimize memory usage by reducing in-memory cover cache size ([@Lolle2000la](https://github.com/Lolle2000la)) ([#2266](https://github.com/mihonapp/mihon/pull/2266))
+- Optimize MAL search queries ([@MajorTanya](https://github.com/MajorTanya)) ([#2832](https://github.com/mihonapp/mihon/pull/2832))
 
 ### Changed
 - Update tracker icons ([@AntsyLich](https://github.com/AntsyLich)) ([#2773](https://github.com/mihonapp/mihon/pull/2773))