can RSS recover from restarts during rack initialization?

There's a lot of work in RSS to make it so that if it restarts while it's running, then it can pick up where it left off and keep finishing rack setup. I think this doesn't work though because bootstrap agent will refuse to run RSS if this sled agent has a ledgered StartSledAgentRequest. More specifically:

When bootstrap agent starts up, it creates a RssAccess::new which either winds up in state Initialized (if a StartSledAgentRequest was found in the local ledger) or Uninitialized (otherwise):
https://github.com/oxidecomputer/omicron/blob/36f6abe06548eae0f954f1b968f98def846f7d93/sled-agent/src/bootstrap/server.rs#L183-L194
https://github.com/oxidecomputer/omicron/blob/36f6abe06548eae0f954f1b968f98def846f7d93/sled-agent/src/bootstrap/rack_ops.rs#L85-L89

Then later if we try to start RSS, we check this state:
https://github.com/oxidecomputer/omicron/blob/36f6abe06548eae0f954f1b968f98def846f7d93/sled-agent/src/bootstrap/rack_ops.rs#L178-L180

and bail out if it's Initialized:
https://github.com/oxidecomputer/omicron/blob/36f6abe06548eae0f954f1b968f98def846f7d93/sled-agent/src/bootstrap/rack_ops.rs#L184-L186

I think the StartSledAgentRequest gets written during RSS here:
https://github.com/oxidecomputer/omicron/blob/36f6abe06548eae0f954f1b968f98def846f7d93/sled-agent/src/rack_setup/service.rs#L918-L929

I think the upshot is that if we make it that far into RSS and then restart, we can't resume. We'll get an "AlreadyInitialized" error even though we haven't finished initialization.

I think we've discussed this elsewhere: it's probably not important that we are able to resume RSS. We could instead factory-reset and just run it again. That currently has issues too though (#3820, #3818).

Start with sled-agent/src/bootstrap/server.rs and sled-agent/src/bootstrap/rack_ops.rs to trace how RssAccess is initialized and why an existing StartSledAgentRequest causes an AlreadyInitialized error. Then inspect sled-agent/src/rack_setup/service.rs around the request write. Determine whether interrupted RSS setup should resume or be rerun after reset, and document the resulting behavior and scope.