Refactor request logging code

add new error type ResourceLimit

Merge branch 'neilj/limit_exceeded_error' of github.com:matrix-org/synapse into neilj/limit_exceeded_error

Neilj/resource limit block event creation

Update the admin register documentation to return a real user ID

Presumably this is the intention anyways. I've also updated the domain part to be something more along the lines of what people might expect.

Fix inbound federation on reader worker

Inbound federation requires calculating push, which in turn relies on
having access to account data.

Changelog should link to PRs

Fix Mau off by one errors

These were removed for the 0.33.2 release, but were incorrectly re-added in

Move more federation APIs to workers

support admin_email config and pass through into blocking errors, 

This involves renaming _persist_events to be a public function.

This commit moves a bunch of the logic for deciding when to log the receipt and
completion of HTTP requests into SynapseRequest, rather than in the request
handling wrappers.

Advantages of this are:
 * we get logs for *all* requests (including OPTIONS and HEADs), rather than
   just those that end up hitting handlers we've remembered to decorate
   correctly.

 * when a request handler wires up a Producer (as the media stuff does
   currently, and as other things will do soon), we log at the point that all
   of the traffic has been sent to the client.

Merge branch 'neilj/update_limits_error_codes' of github.com:matrix-org/synapse into neilj/admin_email

combine mau metrics into one group