Fix lots of nested ands and ors

[dwwoelfel]

Ran into this bug while working on cel -> instaql, where we can generate lots of nested ORs.

Three fixes in this PR:

1. If there's a single AND or OR, then we just strip it out ([{:or [{handle: 'dww'}]}] is the same as {handle: 'dww'})
2. Collapse the ors properly, so that [{:or [{:or [cond-a, cond-b]}, cond-c]]}] generates {:or [cond-a, cond-b, cond-c]} instead of {:or [[cond-a, cond-b], cond-c]}.
3. Fix in datalog.clj to handle ORs in the destination path. I simplified the logic to only do recursion for generating the join conds in one place.

There is still a remaining issue where we could potentially include the same cte twice, leading to postgres complaints about ambiguous columns. I can't reproduce it without disabling the or collapsing, so I'm ignoring it for now. I think it might have something to do with how we generate join syms for the different groups of ors and ands. We might need to increment the level?

[dwwoelfel]

This is still overly complicated--I think it would be a lot easier to reason about if we got rid of the spec coercion, but that's a bigger project.

[stopachka]

Oo, that could be interesting! Would make it nicer too when we print stuff deep inside the codebase

[github-actions]

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[stopachka]

Niice!