One of the optimizations of check-in [de9c86c9e4cdb34f] does not work for

One of the optimizations of check-in [de9c86c9e4cdb34f] does not work for
terms originating in the ON/USING clause, as demonstrated by
[forum:/forumpost/6cf3bb457c3f4685|forum post 6cf3bb457c3f4685].  This
check-in disables that optimization for ON/USING terms.  Also improve the
TreeView display for the resulting "true"/"false" nodes to show that they
originate from the ON/USING clause.  Add a testcase() to the other optimization
to show that it can still be used for ON/USING terms.

FossilOrigin-Name: 1f6796044008e6f3a61bcf390c0c7eb31947e971f0edada74e7a3a211f8ae76a