[amd64,arm64] Enable KEXEC_HANDOVER and LIVEUPDATE

KHO and LUO are new features available on amd64/arm64 that allow seleced runtime state to survive a kexec reboot, added in v6.19. One of the main use cases is letting VMMs quickly resume guests by having their memory transition from one kernel to the next, but there are many others planned, so enable the features at build time.

The feature is disabled at runtime by default unless the cmdline kho=on is specified, so risk for general purpose usage should be very minimal.

https://docs.kernel.org/next/core-api/kho/index.html https://docs.kernel.org/next/core-api/liveupdate.html