Pinot fails or returns incorrect results in case of IS NULL, IS NOT NULL predicates

[findepi]

1. the assumption at

   trino/plugin/trino-pinot/src/main/java/io/trino/plugin/pinot/query/PinotQueryBuilder.java

   Line 127 in dfd38e1

   checkState(!range.isAll()); // Already checked

   
   is incorrect, as this is exactly how Domain.notNull(type) is represented (i.e. result of x IS NOT NULL)
2. the whole io.trino.plugin.pinot.query.PinotQueryBuilder#toPredicate method is incorrect, since it doesn't consult domain.isNullAllowed(), so x IS NULL OR x > 5 is going to return incorrect results

[findepi]

cc @elonazoulay @wendigo @hashhar

[findepi]

cc @elonazoulay

[elonazoulay]

Note:
Pinot does not yet fully handle null values, ex.

select col from table where col is null

will return a non-null default value.

The is not null predicate should not be pushed down.

Will test, may have to disable pushdown of both IS NULL and IS NOT NULL since they will return incorrect results, updating and will push a pr.