Fix test_query_generator for query generation test on each snowflake plan node

[sfc-gh-yzou]

1. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.

2. Please describe how your code solves the related issue.

1. fix a bug in test_query_generator that is was repeated test the query generation on the same plan node
2. use a copy for the alias_map to to use during resolve to avoid unexpected update of the alias map