Add temperature config for high temp warning.

Adds an integer resource (config_warningTemperature) that is used
to display the high temp warning. If it is set to less than 0,
the value from HardwarePropertiesManager#getDeviceTemperatures(
HardwarePropertiesManager.DEVICE_TEMPERATURE_SKIN,
HardwarePropertiesManager.TEMPERATURE_THROTTLING) is used instead.

Test: manual
Bug: 30995038
Change-Id: I05aa1b5930c6c151ebac439dfd5c00b3305dc46d