Use class names instead of plugin IDs

Thankfully BCA doesnt reference IDs statically, i.e config (as in views plugin ID, block IDs), so it makes much sense for us. (Though even if others were to switch to classnames instead of IDs, its possible to shim with aliased classes or add BC ID-detection stuff)

This is a duplicate of ✨ Support FQCN as plugin id Active .

quietone → closed merge request !8693