This commit supports displaying a name for some user that is overrided by the current user, i.e. name annotations.

Type: add

CCBUG: https://iron.lily-is.land/T77

• Verify that unit tests pass.
• Send an account data event with type work.banananet.msc3865.user_given.user.displayname and content {"@tusooa:tusooa.xyz": "小喵风"}. Verify that the display name of the account @tusooa:tusooa.xyz is shown as 小喵风 (tusooa) in:
  • event sender fields
  • typing indicators
  • room member lists
  • titles of user pages
  • notifications