[SPARK-52867][SQL] Remove redundant GetTimestamp

[zml1206]

What changes were proposed in this pull request?

Remove redundant GetTimestamp for ParseToDate when left's dateType is TimestampType and ParseToTimestamp when dateType is the same as left's dateType.

Why are the changes needed?

Simplify plan.

select to_date(t, 'yyyy-MM') from time

before
*(1) Project [cast(gettimestamp(t#7, yyyy-MM, TimestampType, Some(America/Los_Angeles), false) as date) AS to_date(t, yyyy-MM)#9]
+- *(1) ColumnarToRow
   +- FileScan parquet

after
*(1) Project [cast(t#7 as date) AS to_date(t, yyyy-MM)#9]
+- *(1) ColumnarToRow
   +- FileScan parquet

select to_timestamp(t, 'yyyy-MM') from time

before
*(1) Project [gettimestamp(t#7, yyyy-MM, TimestampType, Some(America/Los_Angeles), false) AS to_timestamp(t, yyyy-MM)#11]
+- *(1) ColumnarToRow
   +- FileScan parquet

after
*(1) Project [t#7 AS to_timestamp(t, yyyy-MM)#11]
+- *(1) ColumnarToRow
   +- FileScan parquet

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

No.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

UT.