This includes exposing a new component for configuring the HTTP stack,
as to avoid forcing dependents who have no custom megazord to keep a-s
and a-c versions in sync.
This is required for the CWTS work, and has been coming for a while.
It's a breaking change for users of FxA/Sync/Push who don't megazord
(they must to init HTTP now, and should init rustlog as well). It's also
a breaking change for megazord users, but I'll file PRs for them
individually.
This includes other changes required to update a-s, in logins and fxa
specifically.
