Add --serial option to main program of host controller

fastboot, adb, and tradefed assume ANDROID_SERIAL to be one serial
number, so ANDROID_SERIAL cannot be used to pass multiple serial numbers
to host controller.

The --serial option allows the user to specify a list of serial numbers
for host controller outside the script.

Bug: 71639023
Test: run --serial=
Change-Id: Icb58ac9e57540ebae5efb84307b2c77e5512cb13