[ReadHandler] Analyze Max Timestamp recalculation behavior.

[lpbeliveau-silabs]

Once the Now Timestamps are unified, we need to ensure the current behavior to ignore max in the past won't lead to reports being abandoned by mistake.

[lpbeliveau-silabs]

See comments in https://github.com/project-chip/connectedhomeip/pull/27943/files#r1264326348

[bzbarsky-apple]

Things to think about carefully:

1. The scenario described in those comments, with two handlers, one finishes reporting, we re-schedule things, etc.
2. A scenario where a handler is overdue but we did not schedule a run yet (because we are running late) and a new handler is added.
3. What other cases?