LIN-580 Augment test scaffolding with better guiding examples

[yoonspark]

Summary

This PR builds on the previous bare-bones implementation of pipeline test generation (https://github.com/LineaLabs/lineapy/pull/772) to provide the user with more concrete guiding examples for pipeline testing. Specifically, this PR augments the test scaffold with fuller examples for equality evaluation of each function output (i.e., does each function in the module file generate results as expected?).

Changes

• [x] Flesh out each test method with an example of equality evaluation (i.e., evaluating whether each function in the module produces the same output as expected)
• [x] Save original runtime values of artifacts in the pipeline so that they can be used as “expected“ outputs for testing
• [x] Update module code generation such that each function allows for **kwargs; update existing test snapshots (reverted as per feedback from @lionsardesai)
• [x] Expose test generation as an optional parameter in pipeline-related APIs
• [x] Use LineaPy's warning instead of that from vanilla warnings module
• [x] Add new tests

Testing

Relevant new tests are to be added (COMING SOON).

Ticket(s)

• https://linea.atlassian.net/browse/LIN-580
• https://linea.atlassian.net/browse/LIN-581

[yoonspark]

NOTE FOR REVIEW

This PR includes several files being touched but most are simple test output updates. For code review, you can focus on the following files:

• lineapy/plugins/pipeline_writers.py
• lineapy/plugins/jinja_templates/module_test.jinja
• lineapy/graph_reader/node_collection.py
• tests/unit/plugins/test_writer.py

[yoonspark]

Jotting down thoughts for future work as per discussion w/ @lionsardesai (ordered in priority):

• Reorganize the template structure (e.g., pytest-like parametrization of each test) and/or documentation (e.g., comments, RTD docs) to highlight how the user can update the test to run it on different input and output values.
• For pipeline documentation & tutorial notebooks, use a new example that involves factoring out of common variable(s).
• Add tests to check if the generated test templates run as expected.