Allow to filter properties inside inspector with plugins

[Shinryuuji]

This PR adds EditorInspectorPlugin::filter_property_list(...) which allows a plugin to modify property infos before inspector shows them.

This can be used in different use cases. One of those is if you inherit a core resource like ShaderMaterial, set all shader parameters through code and do not want the user to edit them.

extends EditorInspectorPlugin

func can_handle(object):
	if object is MyShaderMaterial:
		return true;
	return false

func filter_property_list(object, list):
	for p in list:
		if p.name.to_lower().begins_with("shader_param/"):
			p.usage &= ~PROPERTY_USAGE_EDITOR;
	
	return false

This PR might fix #23891, #17122 and #5988.

[groud]

On IRC, @reduz pointed out the fact this has the exact same function as returning false in the parse_property function. See the documentation.

Is there something that differs from this or not ?

[Zylann]

I'm not sure it fixes #5988 in the way I thought, because it involves writing a plugin just to hide a property. It gives the expected result but with more difficulty than overriding get_property_list.

Also, why copy the property list to a script that will likely do the same to remove some of them? Can't it just call a script function returning false so it can just remove elements from the list of properties? In that sense, it's the same as parse_property returning false.

[akien-mga]

As per above comments, it seems that it's more convoluted than the existing possibility to return false in parse_property, and it's not clear whether it solves the referenced issues. Since there are no updates from OP, closing.