SMBus battery (a.k.a. smart battery) enhancement. (#14496)

* Enhancement: State of health, and max_error value is added. Both shows battery health of SMBUS smart battery.
 * Enhancement: BAT_C_MULT parameter is introduced. This is for high-current capable SMBUS-based battery.
As SMBUS only provides 16-bit for current, it could only be +-32768mA which is about +-32A.
But with proper treatment, it could be extended with little accuracy loss.
This factor can be set for individual battery system with available information.
    * Relative SOC introduced. Proper SMBUS battery should provide percentage of remaining battery
directly. Therefore it does not have to be computed like before.
    * State of Health introduced. Proper SMBUS battery should provide SOH value.
    * Max error: this shows estimation error of BMS.
 * Enhancement: With smart battery, precise estimation of time remaining is provided
with impedance track. It is unit of minute, so 60 seconds multiplied.
Update rate of this is not fast, but very useful.

Co-authored-by: Hyon Lim <lim@uvify.com>

msg/battery_status.msg

@@ -17,6 +17,8 @@ uint16 cycle_count         # number of discharge cycles the battery has experien
 uint16 run_time_to_empty   # predicted remaining battery capacity based on the present rate of discharge in min
 uint16 average_time_to_empty   # predicted remaining battery capacity based on the average rate of discharge in min
 uint16 serial_number       # serial number of the battery pack
+uint16 state_of_health	# state of health. FullChargeCapacity/DesignCapacity.
+uint16 max_error # max error, expected margin of error in % in the state-of-charge calculation with a range of 1 to 100%
 uint8 id                # ID number of a battery. Should be unique and consistent for the lifetime of a vehicle. 1-indexed.
 
 float32[10] voltage_cell_v   # Battery individual cell voltages