SNOW-567560 Add split view to Snowpark Python API reference

[sfc-gh-stan]

Please answer these questions before submitting your pull requests. Thanks!

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

   Fixes #SNOW-567560

2. Fill out the following pre-review checklist:

   • [ ] I am adding a new automated test(s) to verify correctness of my new code
   • [ ] I am adding new logging messages
   • [ ] I am adding a new telemetry message
   • [ ] I am adding new credentials
   • [ ] I am adding a new dependency

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

Removed templates that are unused. Used autosummary on functions/exception/attributes/classes directly instead of automodule to generate separate indexed pages. This creates manual work, but automodule does not generate these indexes correctly, which seems to be an open feature request for sphinx-autosummary. On top of that, the team agree we should organize our API's by functionality instead of by module structure, which will also remove most (if not all) usage of automodule.

[sfc-gh-stan]

The warning in Build Doc is caused by an open issue of autosummary. My workaround is to define is_cached as a property, we can revert this once the issue is resolved.