Blender Git Loki

UI: Remember File Browser Display Options in Preferences

This makes it so that some display related properties of the file
browser state are remembered in the Preferences. Otherwise, users often
end up doing the same set up work over and over again, so this is a
nice way to save users some work.
It's typical for other file browsers to remember their state too, so
another benefit is having a more conventional behavior, meeting user
expectations better.

Some points:
* We currently store: Window size, display type, thumbnail size,
enabled details-columns, sort options, "Show Hidden" option. More can
be added easily.
* No changes are stored to the Preferences if "Auto-save Preferences"
is disabled. This is how Quick Favorites behave too and it's a
reasonable way to make this behavior optional.
* The Preferences are only saved to permanent memory upon closing
Blender, following existing convention of Preferences and Quick
Favorites.
* If settings weren't actually changed, Preference saving is skipped.
* Only temporary file browsers save their state (invoked through
actions like open or save), not regular file browser editors. These
are usually used for different purposes and workflows.
* Removes "Show Thumbnails" Preferences option. It would need some
special handling, possibly introducing bugs. For users, this
simplifies behavior and should make things more predictable.
Left in DNA data in case we decide to bring it back.

Reviewers: brecht, #user_interface, billreynish, campbellbarton

Reviewed By: #user_interface, William Reynish, Campbell Barton, Brecht
van Lommel (quick first pass review in person)

Maniphest Tasks: T69460

Differential Revision: https://developer.blender.org/D5893