Push down date literals to Kudu scanner

To reproduce:
explain select * from functional_kudu.date_tbl where date_col = DATE "1970-01-01";

00:SCAN KUDU [functional_kudu.date_tbl]
predicates: date_col = DATE '1970-01-01'

We should see "kudu predicates" instead of "predicates" if it was pushed down.

date is missing from the following switch case, so FE doesn't create kudu predicates for them:
https://github.com/apache/impala/blob/ba4cb95b6251911fa9e057cea1cb37958d339fed/fe/src/main/java/org/apache/impala/planner/KuduScanNode.java#L524

Not sure whether backend changes are also needed