Make it possible to show code hint and code completion at the same time

[chocola-mint]

Fixes #85401

See below demo: (When code completion appears above, code hint is moved below, and vice versa. When there is no code completion, the value of code_hint_draw_below is used to determine where the code hint is)

godot_issue-85401-below.mp4

godot_issue-85401-above.mp4

[KoBeWi]

I think it would be better if the code hint did not change position, but always appear at the opposite side from the completion popup. So it would be at the top by default.

[chocola-mint]

The completion popup is contextual and doesn't necessarily appear where there is a code hint, so it's not a good idea to define code hint's position in terms of the completion popup's position.

If the code hint always appears at the top, then we may have to deprecate set_code_hint_draw_below, as it won't have any effect anymore. Fixing code hint's position also means the position of the code completion is fixed, and won't automatically reposition itself to stay on the screen. So instead, here's a different solution that is hopefully easier on the eyes:

In Visual Studio, the code hint is always placed above, while the code completion automatically repositions itself and may be placed between the edited line and the code hint:

Taking inspiration from Visual Studio, I've made it so the code completion can reposition itself below or above the code hint to fit inside the screen. set_code_hint_draw_below is still used to decide the code hint's position. See below.

godot_issue-85401-below-v2.mp4

godot_issue-85401-above-v2.mp4

[Paulb23]

LGTM, thanks for the contribution!

[YuriSizov]

Applied suggestions and rebased on your behalf.

[YuriSizov]

Thanks!