gui: Add option to hide file extensions

[me25542]

Resolves #4426.

Adds "Show File Extensions" toggle to user interface menu, directly below "Sort Files".

• If this toggle is enabled, behavior is unchanged.
• If this toggle is disabled, file extensions are hid from the file browser, print preview, and printing screens.

Increases RAM usage slightly; at least ~104 extra bytes could be used at any given time.

Tested and seems to work on a MK4S.

BFW-6704

[3d-gussner]

@me25542 Thanks for the PR. Added a comment in the internal ticket.
As it uses quite a bit of extra resources it may become an issue on MINI.

[me25542]

Thanks.
You're right that this might not work on the MINI; resource usage is increased somewhat. However, it does now seem to build OK for the MINI, after some optimizations (it didn't build for the MINI when this PR was first opened), so I don't know for sure.

[me25542]

Extended testing revealed that optimizations made to enable this feature on the MINI broke things, so I have switched to working code, and disabled this feature on the MINI.

[me25542]

I accidentally closed this somehow when updating my branch.