liveupdate: Move to feature flags for LUO and memfd ABI compatibility · v1

Define a 128 byte header that can be used by all live update serialized structures. In this header, we reserve room for 64 features with supported, active, and required bits. Update the top level luo

Create a liveupdate_features section that contains the feature information for a given liveupdate component. Add the LUO component first. These can be compared between two kernels to determine live up

Update struct memfd_luo_ser to embed struct luo_feature_hdr features. Define feature flags for memfd (MEMFD_LUO_FEATURE_SEALS and MEMFD_LUO_FEATURE_FOLIOS), emit the liveupdate feature entry for memfd