This prevents the editor theme from being created twice.
This speeds up the project editor and editor startup
significantly; startup is now 1.3 times faster on average
(tested on a debug build). RAM usage was also lowered by 7.5 MB
on average.
This partially addresses #35321.
Happy new year to the wonderful Godot community!
We're starting a new decade with a well-established, non-profit, free
and open source game engine, and tons of further improvements in the
pipeline from hundreds of contributors.
Godot will keep getting better, and we're looking forward to all the
games that the community will keep developing and releasing with it.
This allows more consistency in the manner we include core headers,
where previously there would be a mix of absolute, relative and
include path-dependent includes.
