Log the snapshot id add it to the plan node for Iceberg queries

For supportability purposes Impala should track the snapshot id that will be used to query the Iceberg table. This could help identify problems like:

• whether two engines are reading from the same snapshots
• trace back which snapshot was read by a specific query. Useful to see if there were any changes between query executions.

The snapshot id could be logged INFO level and added to the query plan tree as well as an attribute of a SCAN node.