atc: flight resource tracks inventory in status

[davidmdm]

This PR ships the following feature: .status.inventory on Flight resources for the ATC.

It however also ships many small improvements to the atc's reconciler logic:

• consistent retries on readiness condition updates
• proper early exit on ready condition update if no change
• check readiness against resources generated via takeoff instead of pulling the latest revision
• readiness polling no longer in background routines but within the reconciliation loop, removing runaway poller goroutines at the cost of more wasm evaluation.