[FEATURE] Build Strategy from Tekton Task/Pipeline

[adambkaplan]

Build strategy authors (ecosystem) will more than likely maintain a Tekton task and/or pipeline as well. Importing a Tekton task or pipeline (ex: from Tekton Hub or a Tekton bundle) as a Build Strategy can reduce duplicated efforts.

Originally posted by @cmoulliard in #1280 (comment)

[adambkaplan]

This feature should be discussed and formalized via a SHIP.

A potential concern is leaking our abstraction of Tekton. Tight coupling of Shipwright to Tekton is already a concern - most recently expressed by TAG App-Delivery in our CNCF Sandbox application.