Fix: build and deploy docs.

[dblock]

Description

Imports in https://github.com/opensearch-project/opensearch-py/actions/runs/6828368821/job/18572361261 are silently failing with this:

WARNING: autodoc: failed to import class 'client.cat.CatClient' from module 'opensearchpy'; the following exception was raised:
No module named 'aiohttp'

1. Added aiohttp to the docs requires.
2. Turned on warnings as errors so we can catch these, and running docs in PRs in the same workflow as the site deployment.
3. Use nox -rs docs everywhere.
4. Ran nox -rs generate with https://github.com/opensearch-project/opensearch-api-specification/pull/165 was merged.

Issues Resolved

Closes https://github.com/opensearch-project/opensearch-py/issues/558.

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[codecov[bot]]

Codecov Report

Merging #575 (a058df0) into main (f1d0237) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #575   +/-   ##
=======================================
  Coverage   71.70%   71.70%           
=======================================
  Files          87       87           
  Lines        7886     7886           
=======================================
  Hits         5655     5655           
  Misses       2231     2231           

Files	Coverage Δ
opensearchpy/_async/client/__init__.py	45.78% <ø> (ø)
opensearchpy/client/__init__.py	61.17% <ø> (ø)