Remove multiapi_combiner (#43642)

* Initial plan

* Remove multiapi_combiner - deleted files, templates, and entry point

Co-authored-by: msyyc <[email protected]>

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Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: msyyc <[email protected]>
Co-authored-by: Scott Beddall <[email protected]>

Author: 3 people