OvmfPkg/EnrollDefaultKeys: split out certificate and signature constants

OvmfPkg/EnrollDefaultKeys: split out certificate and signature constants

A large portion of "EnrollDefaultKeys.c" is hex-encoded X509 certificates,
GUIDs, and signatures. These objects are constants, unlikely to see
changes anytime soon. Move them out of the way, to "AuthData.c", so we can
more easily work on functions in "EnrollDefaultKeys.c".

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien.grall@arm.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1747
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Gary Lin <glin@suse.com>