Add ./task doctest to run Python doctests

[denik]

Why

We have doctests in a handful of Python helpers but nothing runs them. This adds ./task doctest, wired into task test so they run locally and in CI.

It git greps for files containing a >>> prompt and runs the doctest runner on each — importing every Python file blindly fails on generated modules and notebooks that have no doctests anyway.

[github-actions]

Waiting for approval

Based on git history, these people are best suited to review:

• @pietern -- recent work in ./, tools/

Eligible reviewers: @andrewnester, @anton-107, @janniklasrose, @lennartkats-db, @renaudhartert-db, @shreyas-goenka, @simonfaltum

_{Suggestions based on git history. See OWNERS for ownership rules.}

[eng-dev-ecosystem-bot]

Integration test report

Commit: bf30cbd

Run: 30381166736

	Env	❌​FAIL	🟨​KNOWN	💚​RECOVERED	🙈​SKIP	✅​pass	🙈​skip	Time
❌​	aws linux	3	1	3	4	319	1063	6:06
❌​	aws windows	3	1	3	4	321	1061	8:42
❌​	azure linux	3	1	3	4	319	1062	6:02
❌​	azure windows	3	1	3	4	321	1060	6:41
❌​	gcp linux	3	1		5	318	1064	5:59
❌​	gcp windows	3	1		5	320	1062	8:42

11 interesting tests: 4 SKIP, 3 FAIL, 3 RECOVERED, 1 KNOWN

	Test Name	aws linux	aws windows	azure linux	azure windows	gcp linux	gcp windows
🟨​	TestAccept	🟨​K	🟨​K	🟨​K	🟨​K	🟨​K	🟨​K
❌​	TestAccept/bundle/deploy/mlops-stacks	❌​F	❌​F	❌​F	❌​F	❌​F	❌​F
❌​	TestAccept/bundle/deploy/mlops-stacks/DATABRICKS_BUNDLE_ENGINE=direct	❌​F	❌​F	❌​F	❌​F	❌​F	❌​F
❌​	TestAccept/bundle/deploy/mlops-stacks/DATABRICKS_BUNDLE_ENGINE=terraform	❌​F	❌​F	❌​F	❌​F	❌​F	❌​F
🙈​	TestAccept/bundle/invariant/no_drift	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/bundle/resources/vector_search_endpoints/drift/recreated_same_name	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/bundle/resources/vector_search_indexes/recreate/embedding_dimension	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
🙈​	TestAccept/ssh/connection	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S	🙈​S
💚​	TestFetchRepositoryInfoAPI_FromRepo	💚​R	💚​R	💚​R	💚​R	🙈​S	🙈​S
💚​	TestFetchRepositoryInfoAPI_FromRepo/root	💚​R	💚​R	💚​R	💚​R
💚​	TestFetchRepositoryInfoAPI_FromRepo/subdir	💚​R	💚​R	💚​R	💚​R