[3/n] [ls-apis] track sled-agent-rack-setup as a separate subcomponent

[sunshowers]

RSS has very different semantics from the rest of Sled Agent, and the recent split to put it in another crate (#10340) gives us a change to handle this divergence in a principled manner.

Introduce two new notions to ls-apis:

• subcomponents: components that are part of a deployment unit but should be treated separately. Currently, RSS is the only subcomponent.
• lifecycle: when a server component's code runs -- "steady-state" by default, but "rack-init" for RSS

This separation also gives us a chance to do a lot of cleanup within the API manifest:

• the not-deployed evaluation for RSS goes away, since that knowledge can be derived from the rack-init lifecycle
• there's no need for RSS to declare IDU-only edges, since it doesn't participate in the upgrade DAG

Depends on:

• [2/n] [ls-apis] return walked dependencies instead of using a callback #10458

[sunshowers]

Looking for feedback on the inside thing. I tried autodiscovering the inside by looking at the dependency graph but honestly that was a complete mess that was hard to understand both in the code and in this manifest. I feel like having an explicit inside makes both layers easier to understand.