Spun out of SERVER-122001. We should add test coverage for apply_pipeline_suffix_dependencies in pipelines that mix server and extension stages, and verify that transform stages do not receive the callback.

Specifically:
1. Negative test for transforms: Verify that a test extension with a transform stage that overrides applyPipelineSuffixDependencies is not called when the pipeline has a host source stage, since the precondition only matches extension source stages.
2. Mixed pipeline suffix deps: Verify that an extension source stage's suffix dependencies correctly reflect the full suffix including both server and extension stages.

PR context: https://github.com/10gen/mongo/pull/51543#discussion_r3087570645