Chore/user config handling and performance fixes

[Hellgartner]

Summary of changes

Exchange the current setup for using electron settings in the frontend with

• Make sure all of the configuration are always set, this reduces the need for defaults
• Do not use the variables section but create a dedicated redux store for user config
• Sync this store directly at frontend startup -- before any rendering happens
• Register one central handler which forwards any user settings changes to the store
• Using user settings is then only a normal use on the store
• Note that writing user settings from the frontend still requires and IPC call to the backend.

Context and reason for change

The current setup for the user configuration does not scale to the higher number of uses.
Using useUserSetting leads to a lot of

useIpcRenderer(
    AllowedFrontendChannels.UserSettingsChanged, ...

handlers being registered. This has a few unpleasant consequences:

• On any change of any user setting all these handlers fire.
• All these handlers cause a write to the redux store and thus re-renders.
• Hooks for these variables are used in the App.tsx causing re-renders of the entire app on change

This makes even handling small files hard to work with and makes the app crash on larger, more realistic, files.

How can the changes be tested

Full regression test

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[mstykow]

This diff now mixes in changes for classification and criticality that in previous versions were not present. This makes it harder to do a review and I don't think any of this is intended.

[mstykow]

I think we're almost good to go now.