Add hide_titles and hide_icons properties to TabBar & TabContainer

[StarryWorm]

• Closes Add a property to toggle icon & text display in TabContainer godot-proposals#14636

This PR adds two new toggles to TabBar (& TabContainer):

1. hide_titles (& hide_tabs_titles): Hides the titles on all tabs from displaying
2. hide_icons (& hide_tabs_icons): Hides the icons on all tabs from displaying

Below is a summary table (uses a mockup of the editor title bar)

--	Horizontal
show both (default)
hide titles
hide icons

[kitbdev]

• Related Add vertical_mode toggle to TabBar godot-proposals#5031
• See Add support for vertical TabBar and side tab placement on TabContainer #116485

[StarryWorm]

I didn't see that PR, my bad, thanks kitbdev for linking

[StarryWorm]

Changelog:

• Removed the vertical commit, which is handled by Add support for vertical TabBar and side tab placement on TabContainer #116485

[KoBeWi]

I don't see how is this required for something. Editor docks have the same functionality and it's handled by a method that updates the tabs based on preferred style, adding/removing text/icons as needed.

[StarryWorm]

Now that the vertical functionality is removed, that is technically correct.
I still believe this is a good usability improvement, so I will open a proposal to suggest the feature, since it doesn't appear to have been proposed before.

[StarryWorm]

Changelog:

• Added TabContainer functionality
• Renamed hide_text to hide_titles to match existing terminology

[StarryWorm]

Changelog:

• Renamed is_hide_* to is_hiding_* as per ATS' suggestion