scripts/image_signing: Move `extract_firmware_bundle` to common.sh

This commit moves `extract_firmware_bundle` into common.sh as this
function is useful for other scripts as well. This commit also updates
this function to use the `--unpack` option as `--sb_extract` is now
deprecated.

BRANCH=none
BUG=b:202397678
TEST=Verified that scripts continue to work as expected

Signed-off-by: Robert Zieba <robertzieba@google.com>
Change-Id: Ib5596968f31a4b3b21fb81877d84b28660824818
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3665477
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed