more reconfigurator config / chicken switches

[davepacheco]

In principle I think we might want to be able to turn on or off all of the things that the planner does:

• add components (maybe: configure the counts for each kind of thing)
• expunge components
• various upgrade steps:
  • disable SP updates (maybe: individually for sleds, switches, or PSCs?)
  • disable RoT updates (maybe: individually for sleds, switches, or PSCs?)
  • disable zone updates (maybe: each zone type?)
  • disable schema update / handoff

I'm not proposing that we should build all of these switches up front. But I did just run into two bugs that affected:

• only SP updates (would have blocked all update, even if you didn't care about SPs)
• only switch SP updates (same)

That makes me wonder if building some coarse switches up front would be useful if we run into unexpected problems in the field.

[sunshowers]

In today's update watercooler it also came up that:

• we'd like a chicken switch for no-op image source conversions: [24/n] [reconfigurator-planning] support no-op image source updates #8486
• we should make the planner chicken switches testable via reconfigurator-cli