Editor: Inspector and Signal docks improvements

[dalexeev]

• Continuation of Editor: Signal Connection Dock improvements #81092.
• Fixes GDScript 2.0: @export_category interferes with the property inspector tooltip #64432.

1. Fixes a part of #78934 (no description for properties after @export_category).

There is now a way (hint_string) to distinguish type categories from custom categories. This is consistent with scripts, they already use hint_string.

godot/core/object/object.h

Line 492 in 549fcce

p_list->push_back(PropertyInfo(Variant::NIL, get_class_static(), PROPERTY_HINT_NONE, String(), PROPERTY_USAGE_CATEGORY)); \

godot/core/object/script_language.cpp

Line 124 in 549fcce

return PropertyInfo(Variant::NIL, scr_name, PROPERTY_HINT_NONE, path, PROPERTY_USAGE_CATEGORY);

extends Node
@export var a: int
@export_category("Node")
@export var b: int

Also we can make the background a bit less bright than normal categories.

2. Added a tooltip when hovering a class item in the Signal dock, to be consistent with the Inspector.

3. Added "Open Documentation" context menu for classes to Inspector and Signal docks.

4. Fixed a bug with displaying incorrect tooltips for callback items.

Before:

After:

5. Fixed a bug where descriptions could be truncated if they contain :: (the maxsplit argument for String.split() is now specified)

[YuriSizov]

Just a debug print and a bit of cleaning, but code looks good otherwise.

The addition of the hint string seems safe to me, as far as core changes are.

[akien-mga]

Looks good to me.

[akien-mga]

Thanks!