RLS: Add subscription support for 3 and 4 way joins

[joshua-spacetime]

The implementation is described in incremental subscription update proposal.

[egormanga]

I really do need this functionality. Blocks my use-case, although not specifically related to subscriptions, but to one-shot queries through SDK which do require using subs.

Is it possible to work around this limitation at least ad-hoc, by extending the match in question (subscription/src/lib.rs) with 3-way hands?

[egormanga]

Is there a way to use one-shot queries (as opposed to subscriptions) via client SDK to work around this issie for the time being?

[krisajenkins]

See also #5214