Various savestate bugfixes

[PabloMK7]

Fixes a few issues with savestates:

• A class was missing the boost export, so apps with extdata opened at all times (such as the home menu) would fail to serialize.
• RunAsync callbacks are not serializable nor deterministic. Fixed this in two ways:
  • The core will wait for all async callbacks to finish, and then do the savestate. If it takes more than 5 seconds the core throws an error.
  • Added an option to make async callbacks deterministic by not putting them in a new thread. This fixes TASes not working properly depending on load times.
• Disabled savestates when LLE modules are being used. To be figured out why this happens.

[PabloMK7]

@OpenSauce04 this is a large PR, and there is no need to dig deep into it as everything is tested. You can review UI and style changes.