Replace http-addr flag with http-host for consistency

[a-robinson]

Correct me if I'm wrong, but I'd guess we don't want to remove http-addr at the same time that we add http-host, since it'll annoy people and make our docs incorrect for at least some small time period.

I assume it's good enough to add the new flag with precedence over the old one, wait for a new beta release, then update the docs and remove the old one?

As discussed in #9503

@mberhault @sploiselle

[tamird]

It may also be the case that nobody is using http-addr in practice, which would make this simpler.

[sploiselle]

In favor of that plan, @a-robinson. Always prefer gentle deprecation even if it's not much more than a gesture of general good will. Switching it in the docs, assuming it exactly duplicates the functionality, is simple.

Can we include an error message for http-addr that just spits back that it's now http-host? If it's more than nominal effort, think we can get by without it.

[a-robinson]

Adding Sean to get the docs updated with the http-host flag. Once they're updated and a new release has been cut, I'll remove http-addr.