SecurityPkg: Add option to reset secure boot keys.

This commit add option which allows reset content of Secure Boot
keys and databases to default variables.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Reviewed-by: Sunny Wang <sunny.wang@arm.com>
Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>
Reviewed-by: Pete Batard <pete@akeo.ie>
Tested-by: Pete Batard <pete@akeo.ie> # on Raspberry Pi 4