refactor: some Application & style things

[pajlada]

The Updates class is now responsible for connecting to Settings in its constructor. Previously Application did this for it.

The initialized state for Application has been moved to the Application class itself, and is no longer atomic.

The PubSub initialization is now handled by PubSub rather than Application

Global emote reloading on setting toggle is now handled by the respective emote class (e.g. BttvEmotes)

Settings is now initialized slightly earlier to ensure Updates has access to it in its constructor. This shouldn't change anything, but who knows :)

Removed a use of PubSub's setAccount from TwitchChannel. This was extraneous since it's already handled by PubSubManager(previously Application)

stylistic/clang-tidy fixes:
We use the static method of QApplication things where applicable (e.g. QApplication::exec instead of qtApp.exec in Application)

Some static variables were uppercased in ChatterSet/BttvEmotes

Some includes were added/removed

Flattened some anon namespaces (i.e. moved them out of the chatterino namespace)

[github-actions]

clang-tidy made some suggestions