Add ability to sync bookmarks/preview point across difficulties

[Hiviexd]

Resolves #37917

I do plan to add more stuff like syncing volumes and timing, but the latter is better off as its own PR given the complexity/considerations needed on what should the timing sync exactly do to maps. This should be a good start for now.

Adds a timing menu option with a confirmation dialog where you select what you want to sync:

[bdach]

Not how I would have approached this personally. This UI feels very weird because it's adding a facility to synchronize "bookmarks and preview point" on a screen that does not allow manipulating bookmarks or preview point otherwise.

I did not say this out loud but my implicit assumption in proposing timing sync to live on the timing screen was that things like preview point (and bookmarks, I guess, though that never entered the discussion until now) would be visible and manipulable in the timing screen too.

Also does anyone even need the toggles? Is there really a situation wherein you might want sync only one of those?

[peppy]

I think the toggles are a fair way of exposing what is being synced, and giving the option for partial sync for the edge case that's bound to come up.

I do agree the location of this feels a bit out of place. I think it would be better suited implemented as a dialog which could be opened from the menu, or maybe a popover from a location (maybe a few button in the bottom bar or something? Feels more suiting.

[Hiviexd]

Can change it to be a timing menu item with the toggles being in the confirmation dialog.