feat: add the bigframes.bigquery sub-package with a bigframes.bigquery.array_length function

[chelsea-lin]

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Fixes #<issue_number_goes_here> 🦕

[ashleyxuu]

I think the structure is wrong here? It should be parallel with bigframes.ml, bigframes.pandas and start with - items, and we want to name it bigframes.bigquery or Bigquery Built-in Functions?

You can run nox -s docfx to see if it can generate the page for you:

https://g3doc.corp.google.com/devrel/cloud/infra/devrel_services/g3doc/dev/content_automation/cloud_rad/python.md?cl=head#staging-local-changes-from-github-to-devsite to stage docs manually.

[chelsea-lin]

Good catch! It should be fixed. Also check the generated docs from this change: https://bigframes-swe.teams.x20web.corp.google.com/chelsealin/bigframes-docs-2024-04-22/reference/bigframes.bigquery/index.html

[TrevorBergeron]

Lets fix the spelling in the PR title as well

[tswast]

e2e failure: FAILED tests/system/small/ml/test_llm.py::test_create_text_generator_32k_model appears to be unrelated.

[tswast]

Nit: BigQuery

[tswast]

Thanks so much, love it! This is a big milestone and will allow for future expansion of BigQuery SQL APIs, including those without a direct analogue to pandas methods.