Update checked based on the variant type of the value

[Rindbee]

In EditorProperty::update_revert_and_pin_status, if checkable is true, update checked based on the variant type of the value, and rename the function as EditorProperty::update_editor_property_status.

This patch can fix #55455.

Known problems:

1. Unable to check Checkbox for properties of type Object when it is unchecked. This is probably because during value store/fetch, the nullptr (variant type is Variant::OBJECT) eventually becomes Variant() (variant type is Variant::NIL).
2. For theme overrides, click the revert icon will uncheck the Checkbox. This is probably because EditorPropertyRevert::get_property_revert_value returns Variant().

[RandomShaper]

Looks good overall, but I'm not familiar enough with the exact mechanics of theme overriding to be confident to approve.

[Rindbee]

For using Object::get to get theme overrides, the codes involved are as follows:

godot/core/object/object.cpp

Lines 533 to 540 in 066692b

	// Something inside the object... :|
	bool success = _getv(p_name, ret);
	if (success) {
	if (r_valid) {
	*r_valid = true;
	}
	return ret;
	}

godot/core/object/object.h

Lines 389 to 396 in 066692b

	virtual bool _getv(const StringName &p_name, Variant &r_ret) const override { \
	if (m_class::_get_get() != m_inherits::_get_get()) { \
	if (_get(p_name, r_ret)) { \
	return true; \
	} \
	} \
	return m_inherits::_getv(p_name, r_ret); \
	} \

godot/scene/gui/control.cpp

Lines 336 to 365 in 066692b

	bool Control::_get(const StringName &p_name, Variant &r_ret) const {
	String sname = p_name;
	if (!sname.begins_with("theme_override")) {
	return false;
	}
	if (sname.begins_with("theme_override_icons/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.icon_override.has(name) ? Variant(data.icon_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_styles/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.style_override.has(name) ? Variant(data.style_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_fonts/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.font_override.has(name) ? Variant(data.font_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_font_sizes/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.font_size_override.has(name) ? Variant(data.font_size_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_colors/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.color_override.has(name) ? Variant(data.color_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_constants/")) {
	String name = sname.get_slicec('/', 1);
	r_ret = data.constant_override.has(name) ? Variant(data.constant_override[name]) : Variant();
	} else {
	return false;
	}
	return true;
	}

For Control::_get, if theme override exists, fetch the overridden value, otherwise fetch Variant(). Returns true if the prefix matches.

[akien-mga]

Thanks!