Original PR description

Owl 3 turns a component's `props` into an instance field built by `useProps(schema)`, so the static `SomeComponent.props` attribute no longer resolves. The web components whose schema was read from here now export it as a const, so spread that const instead:

    static props = { ...Many2OneField.props }
    props = useProps({ ...many2OneFieldProps })

The owl2 descriptors used by the overriding components are translated to the new `t.*` schema at the same time, and subclasses that only re-declared the parent schema without adding anything simply drop their declaration and inherit it.

Patches that used to extend a component's props through `patch(Comp, {props})` now extend the exported schema directly, since patching the static attribute no longer has any effect.