Improve DataFrame docs flow

[vandit98]

Closes #1397.

Rationale for this change

The DataFrame guide currently mixes the main user flow with lower-level Arrow streaming details, display behavior, and metrics guidance. This makes the page harder to scan for new users who are trying to understand the basic DataFrame lifecycle.

What changes are included in this PR?

• Adds a short roadmap near the top of the DataFrame guide so readers know where the main overview ends and where specialized topics live.
• Moves the detailed Arrow streaming / __arrow_c_stream__ content into a dedicated arrow-interface page under the DataFrame section.
• Replaces the long in-page Arrow section with a compact related-topics section linking to Arrow interface, rendering, and execution metrics pages.
• Adds the new Arrow interface page to the DataFrame section toctree.

Are there any user-facing changes?

Yes, documentation-only changes. The DataFrame docs should be easier to scan and the Arrow streaming content now has a dedicated page.

Verification performed by Vandit:

• git diff --check
• Python sanity check that docs/source/user-guide/dataframe/index.rst links arrow-interface and that docs/source/user-guide/dataframe/arrow-interface.rst exists with the expected heading
• Attempted Sphinx build in a temporary venv with docs dependencies; it stopped on the existing top-level docs/source/index.rst IPython example because the compiled datafusion package was not installed in that temp venv (ModuleNotFoundError: No module named 'datafusion').