[MCC-1476014] Python Lib-Create Fetch_data() function

[afieraru-mdsol]

feature/bug/enhance/refactor/tech_debt/hotfix

• Python Lib-Create Fetch_data() function
• MCC-1476014

Checklist

• Review the pull request to fix typos and ensure variable/function names are intuitive, etc.
• Make sure the pull request does not have excessive number of unnecessary commits. Utilize the git commit --amend --no-edit command to reduce commit messages when making small file changes (like changing linespacing).
• Make sure you have added unit tests for the code changes. Tests should be added in the tests/ folder.
• Modify docs, if required. Add any new documentation in the doc/ folder.
• Rebase on latest active development branch (develop/main).

Changes Summary

• Create fetch_data() function

[Copilot]

Pull request overview

Adds a new/updated fetch_data() API on DataConnectClient intended to retrieve dataset data via Arrow Flight DoGet and return results as a pandas DataFrame, with optional row limiting.

Changes:

• Switches fetch_data() to return pandas.DataFrame instead of pyarrow.Table.
• Adds optional first_n_rows parameter and implements batch-wise streaming conversion to pandas.
• Introduces helper _stream_to_pandas() for record-batch stream → DataFrame conversion.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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