v3.2 brought in some new goodies, although I'm not sure if we can fully
utilise them due to old Vue version.

This IndexedDB wrapper is used for storing the responses received when
querying Thunderstore API for package listings for a specific game.

The refactoring shouldn't be visible to users (except for a minor delay
when storing the response) for now. In short term this allows us to
drop the duplicate in-memory list of ThunderstoreMod objects. In medium
term this aims to make it easier to do further refactorings to deal
with the poor performance of handling the very large mod lists in
communities like Lethal Company.

The process of accessing the list of mods available via Thunderstore
API for a specific game:

1. Components (SplashMixin on the foreground and UtilityMixin on the
   background) trigger the API request, currently via
   ConnectionProvider
2. Components pass the response to ThunderstorePackages which writes
   the results to IndexedDB. ThunderstorePackages module might become
   obsolete in the future
3. Components trigger Vuex update where TsModsModule reads the mod list
   from IndexedDB and stores it in memory
4. Component access the list via Vuex

To keep the commit size down ModBridge and ThunderstorePackages'
internal methods still use the duplicate PACKAGES and PACKAGES_MAP
objects, but those will be cleaned out in the subsequent commits.

The methods isn't really used much and this allows us to drop the
dependency on the soon obsolete ModBridge.

Implement cached "ManifestV2 to ThunderstoreMod" conversion in
TsModsModule in a way that's compatible with what ModBridgre did
previously. This allows us to drop ModBridge, and the duplicate
in-memory list of PACKAGES.