Re: Duplicate Workers entries in some EXPLAIN plans

Thanks for the review! I looked at <b925a00f4ef> and rebased the patch
on current master, ac5bdf6.

I introduced a new test file because this bug is specifically about
EXPLAIN output (as opposed to query execution or planning
functionality), and it didn't seem like a test would fit in any of the
other files. I focused on testing just the behavior around this
specific bug (and fix). I think eventually we should probably test
other more fundamental EXPLAIN features (and I'm happy to contribute
to that) in that file, but that seems outside of the scope of this
patch.

Any thoughts on what we should do with text mode output (which is
untouched right now)? The output Andres proposed above makes sense to
me, but I'd like to get more input.