Boot control HAL based on the A/B headers.

The added bootctrl.bcb module implement the legacy interface for the
bootctrl HAL based on the Boot Control Block (BCB) and the headers
already specified in the booloader_message library.

This serves as a reference implementation of the boot_control HAL.

Bug: 32707546
Test: Tested internally that a device can use this HAL to flip slots and
recovery from a /misc wipe.

Change-Id: Ic02e5aaf4de7d0a1780eac4e8705dae20d0b3e10