[SPARK-56391] [SQL] Support unwrap string type to date type in UnwrapCastInBinaryComparison

[daijy]

What changes were proposed in this pull request?

Improve the existing UnwrapCastInBinaryComparison to unwrap string to date, ie. cast(date_key_string as date)=date_literal_constant => date_key_string=cast(date_literal_constant, string)

Why are the changes needed?

Spark fail to push date_key_string=date_literal_constant condition to iceberg table, this works fine for parquet table (date_key is a string partition column):

explain select date_key, count(*) from roku.fact_device_log_amoeba_events_hourly where date_key=date_add(current_date, -10) group by date_key;

== Physical Plan ==
AdaptiveSparkPlan isFinalPlan=false
+- HashAggregate(keys=[date_key#25], functions=[count(1)])
   +- Exchange hashpartitioning(date_key#25, 200), ENSURE_REQUIREMENTS, [plan_id=16]
      +- HashAggregate(keys=[date_key#25], functions=[partial_count(1)])
         +- Filter (cast(date_key#25 as date) = 2026-03-28)
            +- BatchScan spark_catalog.roku.fact_device_log_amoeba_events_hourly[date_key#25] spark_catalog.roku.fact_device_log_amoeba_events_hourly (branch=null) [filters=date_key IS NOT NULL, groupedBy=] RuntimeFilters: []

The reason is Spark add a cast on the left side to cast string to date. The cast expression pushed to iceberg data source which is not able to process. A workaround is to add cast on right side, ie. cast date to string.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Unit test

Was this patch authored or co-authored using generative AI tooling?

claude-4.5-sonnet