Add get_property_list to gdextension classes

[lilizoey]

To dynamically update properties in Godot you must override get_property_list (_get_property_list in gdscript). This is a special-cased virtual method that doesn't show up along normal virtual methods, so we do not support this currently.

This method however does require returning a pointer to a property list, and there isn't a good way to get the length back when godot asks us to free it. See godotengine/godot-proposals#9462 for an upstream issue that proposes a fix to this feature.

#621 is a PR that tried to implement this initially, however im closing that for now and opening this issue instead to track that.

Additionally property_can_revert and property_get_revert should also be implemented so people can set custom reverts for properties.

[Bromeon]

Upstream PR to unblock: godotengine/godot#91179

[Bromeon]

Upstream has been merged.