Support more general tasks inside engine

[liamfallon]

Original issue URL: kptdev/kpt#3272
Original issue user: https://github.com/mortent
Original issue created at: 2022-05-27T22:31:46Z
Original issue last updated at: 2022-05-27T22:31:46Z
Original issue body: There are api-level tasks but also tasks created by the engine, such as:

• rendering a package
• creating deployable instance
• (future) applying guardrails

Update interface to handle the broader set instead of reusing the limited API task struct.

Original issue comments:

[liamfallon]

To be considered in rearchitecture discussions.