fix(functions): list schedules with function external id

[MortGron]

Description

Specifying function_external_id in schedules.list always return an empty list even though schedules exists:

Pytest has been updated to v9 to support subtests

Checklist:

• Tests added/updated.
• Documentation updated. Documentation is generated from docstrings - these must be updated according to your change.
  If a new method has been added it should be referenced in cognite.rst in order to generate docs based on its docstring.
• The PR title follows the Conventional Commit spec.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.06%. Comparing base (56aa085) to head (ae0d23a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2783      +/-   ##
==========================================
+ Coverage   93.03%   93.06%   +0.03%     
==========================================
  Files         515      515              
  Lines       53006    53017      +11     
==========================================
+ Hits        49313    49340      +27     
+ Misses       3693     3677      -16     

Files with missing lines	Coverage Δ
cognite/client/_api/functions/schedules.py	88.23% <100.00%> (+0.93%)	⬆️
cognite/client/_sync_api/functions/schedules.py	96.87% <ø> (ø)
tests/tests_integration/test_api/test_functions.py	86.61% <100.00%> (+0.66%)	⬆️

... and 6 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[gemini-code-assist]

Code Review

This pull request updates the function schedules listing API to retrieve and filter by a function's internal ID when an external ID is provided, returning an empty list if the function is not found. It also bumps the pytest dependency to >=9 and adds integration tests for these changes. However, the new tests introduce the subtests fixture, which requires the pytest-subtests package that is not declared in the project dependencies.

[haakonvt]

@HMEiding could you take a quick look on this one?