Shut down detector heaters cleanly when cryostats are warm

The detector heater loops currently do not shut down when the cryostat reaches room temperature. No harm in that, but we would still like to define the expected behavior and to turn the heater off. After the 2024-09 warmup we (yuki.moritani and cloomis) settled on shutting the heater loop down when the detector sensor reaches some plausible threshold (default=275K) and the system reaches equilibrium (max temp - min temp < 2K).

Have added two configuration knobs: warmLimit and warmBand set as above.

Also raised the safety headroom for the detector above the coldest other sensor from 5K to 7K.