Fixes microsoft#53967

The problem is that the weird, ad-hoc CJS merge needs to happen at two different
times.  The first is its existing location in getCommonJsExportEquals.
The second is getResolvedMembersOrExportsOfSymbol, which combines
normal, early-bound symbols with late-bound symbols.

The CJS merge happens before the addition of late-bound symbols, so a
merge will result in the loss of [Symbol.iterable] from the bug.
But manually merging the resolvedExports/Members during the CJS merge
also doesn't work, because it prevents the module's
resolvedExports/Members from being filled in later.

Instead, this PR delays part of the CJS merge to
getResolvedMembersOrExportsOfSymbol. Unfortunately, this requires
retrieving the original, unmerged symbols--since their
resolvedExports/Members are already cached. I do this by looking at the
symbols for each of the merged symbol's declarations, which feels wrong.

Please suggest alternate ways to do this. I don't think I understand the
late-binding machinery well enough, so it's likely there's a cleaner
way.