vboot_reference: Add support for 3072-bit exponent 3 keys

This also adds the required tests (keys, testcases), and some
additional tests in vb2_rsa_utility_tests.c that were not
added when 2048-bit exponent 3 support was added.

BRANCH=none
BUG=chromium:684354
TEST=make runtests

Change-Id: I56d22302c2254ef500b9d2d290a79d8c8bc39942
Reviewed-on: https://chromium-review.googlesource.com/449060
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
21 files changed