Nexus should pass request for "all datasets on a sled" as a single endpoint with a generation number

[smklein]

#2972 (comment) for some context, but it basically would let the "local ledger of services" on a sled be more cleanly a cache of data from CRDB.

[davepacheco]

I think this is obviated now that datasets and services are the same API and we already have #2977. Is that right @smklein?

[smklein]

Unfortunately still missing a generation number

[davepacheco]

But is it now covered by #2977 since datasets and services are the same endpoint now?

[davepacheco]

I think this is obviated by #4466.