SecurityPkg: limit verification of enrolled PK in setup mode

SecurityPkg: limit verification of enrolled PK in setup mode

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2506

Per UEFI spec, enrolling a new PK in setup mode should not require a
self-signature. Introduce a feature PCD called PcdRequireSelfSignedPk
to control this requirement. Default to TRUE in order to preserve the
legacy behavior.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Co-authored-by: Matthew Carlson <macarl@microsoft.com>
Signed-off-by: Jan Bobek <jbobek@nvidia.com>
Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>