Finish masking HashTableLookup accord with the spec.
* No input plan node.
* Can do several equality conditions, but does not need to do them all.
* Whatever conditions it does do not appear as join conditions, but rather as hash columns.
* Operator checks row type matches that of the hash table.
* Improve the cost estimation a little; in particular row counts.
* Only attempt hash join when best plan doesn't have an indexed join condition.
Update RulesTest expected plans for the changes.