Clean up longstanding API warts and pending breaking changes

With 1.0 looming, should we track down any other breaking changes and API warts and just do them?

Things I can think of off the top of my head:

• experimentalPrivilegedNesting <- we talked about just making this always-on
• experimentalWithAllGPUs <- did the experiment succeed?
• experimentalWithGPU <- do we need BOTH of these?

• * experimentalDaggerRunnerHost | * daggerCloudEngine (not experimental but needs revisiting) - done by @shykes.

• LLM APIs are being redone with #13634 and #13635

Any others?