SNOW-1893939: Add support for Index.drop_duplicates

[sfc-gh-amaheshwary]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-1893939

2. 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.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines

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

   Added support for Index.drop_duplicates.

[github-actions]

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[sfc-gh-amaheshwary]

I have read the CLA Document and I hereby sign the CLA

[sfc-gh-nkrishna]

Some minor suggestions around adding more tests, but LGTM overall

[sfc-gh-nkrishna]

LGTM! Nice work :)

[sfc-gh-jjiao]

Great job for your first PR!

[sfc-gh-helmeleegy]

You'd also need to remove references to drop_duplicates in test_unimplemented.py. But looks good otherwise. Congrats on the first PR :)