Add test cases for UPSERT. And a fix for a "REPLACE INTO ... ON CONFLICT"

statement where the new row conflicts with both the IPK and the ON CONFLICT
indexes.

FossilOrigin-Name: d8eb9f8d9b61400c7e12f01ef5c233257b03532221f7c7a8386f7ac2db439626

src/insert.c

@@ -1496,7 +1496,7 @@ void sqlite3GenerateConstraintChecks(
     assert( OE_Abort<OE_Replace );
     assert( OE_Rollback<OE_Replace );
     if( onError>=OE_Replace
-     && onError!=overrideError
+     && (pUpsert || onError!=overrideError)
      && pTab->pIndex
     ){
       sAddr.ipkTop = sqlite3VdbeAddOp0(v, OP_Goto)+1;