Instead of using bitflags, this reimplements the status code struct by
hand. Using bitflags has some unfortunate side effects in that it makes
the debug implementation completely wrong. This way we get a much richer
implementation of the status code, which is also more correct.

This includes a validate method, which might be handy, but it is not enforced
anywhere.

The implementation uses some relatively simple declarative macros, so
the old JS script used for codegen is removed.

It is now possible to establish a connection, end to end, using the
async client and async server. Next up is writing framework code for
services, then implementing the existing in-memory node manager.

This one is more correct, but this got very complex. Probably worth
splitting into its own module and perhaps finding some way to improve
code clarity at some point.

In general the change is good though, I think.

This service is a nightmare with this design. Hopefully things will get
a lot simpler once we get away from browse.

Pretty much just empty impls for now, but the stuff in the node manager
is at least really simple, which is good.

This should, maybe, fix the one remaining hole in that implementation.

Finally finishing up the core logic, just need to implement services and
node manager functionality.

Next is handling monitored items

This is potentially slightly less efficient (though node managers still
have the ability to make it efficient, and likely will in most normal
circumstances), but it greatly simplifies implementing node managers
which is good.

Just basic implementations, as the in-memory-node-manager doesn't do
much with these by default.

Just some free perf I realized we could get easily here.

This thing may need some more work, it also means that having multiple
sessions in a single transport won't work properly.

Should go through server config, generally.