Add a command to get the minimum battery voltage required for flashing

Bug: 79480454
Test: fastboot getvar battery-soc-ok

Change-Id: I6141993972a3084fe3620d81f707999e1264b997
Merged-In: I6141993972a3084fe3620d81f707999e1264b997
(cherry picked from commit 83f5631d)