R1:e5b923743a13

Make CSRF salt per-user instead of per-request

Summary:
Fixes T8326. This removes calls to PhabricatorStartup from places that daemons may access.

This salt doesn't need to be global; it's embedded in the token we return. It's fine if we use a different salt every time. In practice, we always use the same viewer, so this change causes little or no behavioral change.

Ref T8424. For Spaces, I need a per-request cache for all spaces, because they have unusual access patterns and require repeated access, in…