Add a new initramfs hook for running tests in a CI environment.
This hook automatically runs any scripts from /usr/libexec/ci-tests.
Tests should be installed as a subpackage of some other package (e.g.
qrtr) with an install_if clause to install them when this hook is
installed.
This allows platform specific packages like device packages to define
tests that will automatically be installed and executed when building
the initramfs for that device. See
device/community/device-oneplus-enchilada for an example.
Signed-off-by: Caleb Connolly <caleb@connolly.tech>
