Spaces power level sync

[novocaine]

It's currently difficult for Spaces admins to admin subspaces and room in spaces they've created - they won't necessarily be admins in such sub-rooms, so won't have the power to moderate. In many contexts, its expected that Space admins will have this sort of power.

• There should be a way for Space admins to have cascading synchronised power levels in subspaces and rooms
• There should be a way for a Space admin to kick/ban a user from a space and all its rooms
  • Allow options to cascade kicks/bans throughout spaces matrix-org/matrix-react-sdk#6829

Related MSCs

• MSC2962: Managing power levels via Spaces matrix-org/matrix-spec-proposals#2962
• MSC3216: Synchronized access control for Spaces matrix-org/matrix-spec-proposals#3216