Sort variables in VisualScriptEditor

[raulsntos]

Sorts the script variables in alphabetical order to display them in VisualScriptEditor.

The variables are sorted in 3.x because get_variable_list returned the list already sorted but this was changed in #39649.
This PR sorts the variables after retrieving them in VisualScriptEditor instead of directly in get_variable_list so this works like the functions (also retrieved unsorted with get_function_list and then sorted by VisualScriptEditor).

Closes #58509

[fire]

Looks good.

[fire]

Question, do we want to use Unicode sorting? @bruvzg Any ideas?

[bruvzg]

Question, do we want to use Unicode sorting? @bruvzg Any ideas?

There's no easy solution. We can use ICU collation API. But it will depend on a specific text server implementation, and probably will need more data. I need to re-check it, but I'm pretty sure I have stripped it from the data file currently used.

[fire]

Sounds difficult, but Unicode sorting doesn't block this.

[akien-mga]

Thanks!