ColorPicker remove unused children and fix sample bugs.

[WhalesState]

• Fixes: Pressing the ColorPicker's sample left half side changes the color to black when old color is not displayed. #88073

Remove an unused VBoxContainer.
Remove a redundant VBoxContainer and add it's children directly to main vbox.
Remove 3 unused children from grid (Label, Slider, SpinBox).
Fix current color overbright position.
Added color mode buttons and sliders to a another VBoxContainer to hide both when sliders_visible is false.
Use tab_hovered instead of tab_pressed when hovering a mode button.

[KoBeWi]

Pretty sure changing base type breaks compatibility, which is why the redundant VBoxContainer had to exist.

[WhalesState]

Pretty sure changing base type breaks compatibility, which is why the redundant VBoxContainer had to exist.

What is the use case of the MarginContainer ? if for the color button popup, then why don't we include the margins inside the popup's panel ?

[WhalesState]

Reverted the base class to VBoxContainer again, it's easier to be reviewed now.

[KoBeWi]

What is the use case of the MarginContainer?

The "use case" is that ColorPicker doesn't need to be used with popup. It's a stand-alone node, ColorPickerButton only wraps it.
The container was added in #78468

[WhalesState]

Check the title, should i open a new issue for each fix to track them?

[KoBeWi]

There is a behavior change, which is questionable. Everything else looks fine.

Check the title, should i open a new issue for each fix to track them?

I think it's ok, but the sliders_vbox deserves its own issue/PR.

[WhalesState]

Applied all the suggestions.

[Repiteo]

Thanks!