This is bluntly backported from https://github.com/matrix-org/synapse/pull/12853/files
Cherry picking was deemed too complex for that change since it is
split in 5 commits.

This reverts commit 89f478a9.

Issue was closed upstream: https://github.com/matrix-org/synapse/issues/6211

This reverts commit 4d7807ee.

* Fix bug /sync returning 404

Fixes #12571

Add the `update_user_directory_from_worker` configuration option (superseding `update_user_directory`) to allow a generic worker to be designated as the worker to update the user directory. (#12654)
Co-authored-by: Shay <hillerys@element.io>

Otherwise it can take up to a minute for any in-flight `/send` requests to be retried.

Fixes vector-im/element-web#20788
Implements matrix-org/matrix-spec-proposals#3786

* Bump the HS startup timeout
* Log prefixes for more processes
* Bump the overall timeout

There's no guarantee that module callbacks will handle cancellation
appropriately. Protect module callbacks with read semantics from
cancellation and avoid swallowing `CancelledError`s that arise.

Other module callbacks, such as the `on_*` callbacks, are presumed to
live on code paths that involve writes and aren't cancellation-friendly.
These module callbacks have been left alone.
Signed-off-by: Sean Quah <seanq@element.io>

#12587 has fallen on the wrong side of the release cutoff to the rest of
the related PRs.
Signed-off-by: Sean Quah <seanq@element.io>

Fixes #12669