Delay syntax validation while caret moves.

[Lexyth]

Currently, the syntax validation considers you to be done with what you were typing when you're not typing for a second.
This can lead to "work-in-progress" being marked as invalid before you're actually done with it, if, for instance, you're only moving the caret to another region of the word/statement.

As an example, changing any type to or from an Array version of that type marks the line as invalid while the caret is being moved in position to add/remove the closing bracket.

Delaying the syntax validation until the user is done with typing AND moving the caret should more accurately reflect being done with the interaction as a whole.

Eg.: Delay validation by 1 second after you released any key, including arrow keys.

[Calinou]

This seems to be how VS Code works, so it makes sense to do the same in Godot:

vscode_error_lens_caret_movement.mp4