Verbose feedback when loading a save

[EnigmaticAussie]

TL;DR: add an option which displays to the user what the game is actually doing when loading a save.

What:

When loading a large save, with many mods, and the `on_configuration_changed` event fires - I would like to know that the game is running through migrations and configuration changes - perhaps for which mod - instead of just hoping that the game is still processing something when the loading progress bar is at 100%.

Why:

I like data - having visual feedback that the game is processing is helpful when dealing with large saves and multiple mods.