### What changes were proposed in this pull request?
The SQL function TO_TIMESTAMP should return different results based on the default timestamp type:
* when "spark.sql.timestampType" is TIMESTAMP_NTZ, return TimestampNTZType literal
* when "spark.sql.timestampType" is TIMESTAMP_LTZ, return TimestampType literal
This PR also refactor the class GetTimestamp and GetTimestampNTZ to reduce duplicated code.
### Why are the changes needed?
As "spark.sql.timestampType" sets the default timestamp type, the to_timestamp function should behave consistently with it.
### Does this PR introduce _any_ user-facing change?
Yes, when the value of "spark.sql.timestampType" is TIMESTAMP_NTZ, the result type of `TO_TIMESTAMP` is of TIMESTAMP_NTZ type.
### How was this patch tested?
Unit test
Closes#33280 from gengliangwang/to_timestamp.
Authored-by: Gengliang Wang <gengliang@apache.org>
Signed-off-by: Max Gekk <max.gekk@gmail.com>
(cherry picked from commit 32720dd3e1)
Signed-off-by: Max Gekk <max.gekk@gmail.com>
4e9e2f32e8