The existing HAL has a setter, but no getter for the active slot for
next boot. The information is useful. For example, clients may need
to figure out which build the device will boot into.
In the resume on reboot case, we want to put the vbmeta digest
together with an encrypted key. And the vbmeta digest is associated
with a set of images (depending on which slot to boot into).
Bug: 173808057
Test: run vts test on cuttlefish
Change-Id: Ia8578926c781eb8e006589f45ab35a95dfe4f9a0
It should belong to the default /misc implementation of boot control
1.1. Right now, the library as well as the bootloader_message_ab
are only used by cuttlefish. So move it over to reduce the confusion
in libbootloader_message.
Bug: 131775112
Test: build
Change-Id: I599678bf90d19718de811b9e34d82cf8fe1571a4