Minor Description
As discussed in https://github.com/apache/spark/pull/33115#discussion_r659866760, it is more convenient to have a new data type "AnyTimestampType" instead of using type collection `AllTimestampTypes`:
1. simplify the pattern match
2. In the default type coercion rules, when implicit casting a type to a TypeCollection type, Spark chooses the first convertible data type as the result. If we are going to make the default timestamp type configurable, having AnyTimestampType is better
