cgptlib: Make IsBootableEntry available for depthcharge

Make IsBootableEntry, IsAndroid and IsChromeOS functions available for
depthcharge, so fastboot code can distinguish different kinds of
bootable partitions.

BRANCH=main
BUG=None
TEST=Build AP FW

Change-Id: I6561e121b934c52e811254185e7b91c392f8ff96
Signed-off-by: Tomasz Michalec <tmichalec@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/6728037
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
(cherry picked from commit 9b362962860caef101b6d11debd2dd6366a2d274)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/6914586
Tested-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-by: Konrad Adamczyk <konrada@google.com>
Commit-Queue: Konrad Adamczyk <konrada@google.com>
Auto-Submit: Nick Vaccaro <nvaccaro@google.com>