The Pixel 2 system images release was a bit of a disaster because anyone
using an old version of fastboot would blindly flash too few partitions,
potentially bricking their device. This change lets us add a line to
the android-info.txt file for a device with a new partition.
Also error out sooner in such cases by checking the requirements
immediately, rather than optimistically unpacking everything first.
Switch Action over to C++ to fix memory issues.
Bug: http://b/77158188 (partition checking)
Bug: http://b/74444116 (error out sooner)
Test: manual testing with a modified android-info.txt
(cherry picked from commit 5620d224b6)
Change-Id: Ib97af6f9392f7672430ff71228484e6ee7af6fbf
