Ensure that all ON CONFLICT REPLACE indexes are sorted to the end of the list

Ensure that all ON CONFLICT REPLACE indexes are sorted to the end of the list
of indexes for a table, even for weird cases where the same UNIQUE constraint
occurs twice with the ON CONFLICT REPLACE clause only on the second one.  This
avoids an out-of-order contraint processing problem that can arise due
to the optimization of check-in [469a62ca33081854].

FossilOrigin-Name: 1e3918ca2f2c1cfcfa44249b1d7b847d52cbb8d302a8d4a335c090cfdf22d7a1