Support UEFI SecureBoot within OpenCore

[vit9696]

It is reasonable to implement UEFI SecureBoot within OpenCore, so that one can provide Linux and Windows CA inside config.plist instead of falling back to UEFI PE loader. This would give us:

• better firmware security as there can be multiple hidden bugs within each firmware implementation.
• testing of our new upcoming PE loader on more operating systems.
• simplification of the SecureBoot configuration for the end users, as they would only need to sign OpenCore and their OptionROMs with a custom certificate and a couple of hashes. It would be possible to add all the operating systems with just a few config.plist edits and revaulting.