Support limit query in Redshift UNLOAD

[mayankvadariya]

Currently Redshift unload doesn't support limit clause directly and hence trino-redshift also doesn't support limit clause to be executed through unload flow, rather limit clause queries fallback to JDBC flow. However, Trino can implement the workaround of wrapping limit clause query in an inner query as suggested in unload docs https://docs.aws.amazon.com/redshift/latest/dg/r_UNLOAD.html

[findinpath]

If we are using LIMIT is there any need for UNLOAD ?

UNLOAD is supposed to be used in scenarios where we care about the delivery speed of large responses.
LIMIT seems to be more suitable for traditional resultset-based retrieval scenarios.