Add windows which ARI renewal intervals avoid

We have two categories of times that we would like ARI renewals to "avoid" (perhaps by constraining the jitter interval added in #8576)

• Recurring peaks, especially at UTC midnight

• Planned maintenance windows, which are time periods when we know we're going to have some reduced capacity

I'm not sure what exactly the right way to configure this is, but even without a firm design I figure we could start with a ticket to brainstorm ideas.

Eg, if the jitter window overlaps with a configured peak time or maintenance window, we could constrain the jitter window to whichever side is bigger. Or perhaps just always prefer to move it to the "sooner" side. Or we might want to move the jitter window instead of constraining it.

Start by reviewing the jitter work in #8576 and the current ARI renewal scheduling entry point; the issue names no files or tests. Clarify how recurring UTC-midnight peaks and planned maintenance windows should be configured and how overlapping jitter windows should move, then define tests and acceptance criteria for the chosen design.