Add a separation layer for save/load/clear to ManageTokensModel
so that we can save/load from external sources.
The separate layer is composed of JSON as protocol, a set of signals
and slots for interface. The implementation forwards data to current
QSettings for storybook and nim controllers for the app.
Updates #13313, #13312
- reduce the duplication by moving the controllers (1 per type) to the
toplevel stores
- make sure the internal properties stay in sync between save/load now
that we have just 1 common controller
- fix navigating to the Hidden section from the toast
- finish impl of hiding the token from FirstTokenReceivedPopup
put the respective controller instances into WalletAssetsStore and
CollectiblesStore, so that they can be accessed from other places, like
the SendModal or some popups
Iterates #13293