The general idea here is to get rid of the type: ignore annotations on all of the current_token and update_function assignments, which would have caught #7290.

After a bit of experimentation, it seems like the least-awful way to do this is to pass the offending functions in as parameters to the Stream constructor. Unfortunately that means that the concrete implementations no longer have the same constructor signature as Stream itself, which means that it gets hard to correctly annotate STREAMS_MAP.

I've also introduced a couple of new types, to take out some duplication.

Some of the query functions return generators rather than lists, so we can't
index into the result. Happily we already have a copy of the results.

(think this was introduced in #7024)

We could end up looking up tens of thousands of events, which could cause large
amounts of data to be logged to the postgres log.

This commit was originally merged in #7228 but reverted in #7254 as the
associated sytest was not ready yet. Now that it is, we can merge this
again.

This reverts commit 59f0ca8b.

I don't really remember why this was so complicated; I think it dates
back to the time when we had to instantiate the Config classes before
we could call `add_arguments` - ie before #5597. In any case, I don't
think there's a good reason for it any more, and the impact of it
being complicated is that `--help` doesn't work correctly.

We pass --daemonize on the commandline, which (since at least #4853) overrides
whatever the config file, so there is no need for it to be set in the config
file.

Simplify and update this documentation, and make it part of the core dist.

We seem to have some duplicates, which could do with being cleared out.

Miscellaneous cleanups to replication code

`REPLICATE` is now a valid command, and it's nice if you can issue it from the
console without remembering to call it `REPLICATE ` with a trailing space.

Separate `SimpleCommand` from `Command`, so that things which don't want to use
the `data` property don't have to, and thus fix the warnings PyCharm was giving
me about not calling `__init__` in the base class.

We've ripped pretty much all of this out: let's remove the remains.

* Fix typo in the login fallback javascript

* Changelog

They just get in the way.

Fixes a race between handling `POSITION` and `RDATA` commands. We do this by simply linearizing handling of them.

This completes the merging of server and client command processing.