set-verity-state: Add -h -v -R (automatic reboot) options

-h: print help
-v: noisy output
-R: automatic reboot if needed

Also remove the "argc != 0" check, as this shouldn't happen most of the
time anyway. The only possible way (I can think of) for this to happen
is to explicitly call execve() with an empty argv, which is against the
calling convention, thus a footgun, to begin with.

Bug: 241688845
Test: adb shell [disable-verity|enable-verity] [-R] [-v] [-h]
Test: adb shell set-verity-state [-R] [-v] [-h] [0|1]
Change-Id: I27fc18b0958650c5926322a3f4bd1df758fd96c8