Also start organizing editor-specific GUI components
into a dedicated folder, `editor/gui`.
Also move `editor_file_server` next to the rest of debugger classes.
* This solution is much cleaner than the one in 3.x thanks to the use of callables.
* Works without issues in any language (no need to worry about camel or snake case).
* Editor code uses a compatibility function (too much work to redo).
Fixes#59899
As many open source projects have started doing it, we're removing the
current year from the copyright notice, so that we don't need to bump
it every year.
It seems like only the first year of publication is technically
relevant for copyright notices, and even that seems to be something
that many companies stopped listing altogether (in a version controlled
codebase, the commits are a much better source of date of publication
than a hardcoded copyright statement).
We also now list Godot Engine contributors first as we're collectively
the current maintainers of the project, and we clarify that the
"exclusive" copyright of the co-founders covers the timespan before
opensourcing (their further contributions are included as part of Godot
Engine contributors).
Also fixed "cf." Frenchism - it's meant as "refer to / see".
