Change avatar to use Compound implementation (#11448)
* Move avatar to new compound implementation
* Make space avatars square
* Remove reference to the avatar initial CSS class
* remove references to mx_BaseAvatar_image
* Fixe test suites
* Fix accessbility violations
* Add ConfirmUserActionDialog test
* Fix tests
* Add FacePile test
* Fix items clipping in members list
* Fix user info avatar sizing
* Fix tests
