Now that MSC1772 passed FCP its identifiers have stabilised
This outright drops support for experimental spaces but that's what you get for being on the bleeding edge
* Add fedsender dep on msc2946
* Add MSC2946Spaces to fsAPI
* Add exclude_rooms impl
* Implement fed spaces handler
* Use stripped state not room version
* Call federated spaces at the right time
* Add stub functions for MSC2946
* Implement core space walking algorithm
* Flesh out stub functions; add test stubs
* Implement storage bits and add sanity check test
* Implement world_readable auth with test
* Linting
Michael Telatynski
Neil Alexander
Kegsay