CP-32446: Introduce Xen.features_pv_host and Xen.features_hvm_host
CP-32446: Introduce Xen.features_pv_host and Xen.features_hvm_host

The existing `features_hvm` and `features_pv` will continue to report
migration-safe CPUID flags.

The new fields will report the pool-leveling and VM boot-time CPUID flags.

There are certain CPUID features that are not present on the host, but still work
after a migration, albeit slowly: these will be present in `features_hvm`,
but absent from `features_hvm_host`.

Signed-off-by: Edwin Török <c8d178016cbaf8a6ef23c2cbc9db96123c48b7dc@citrix.com>

xapi-project/message-switch,xapi-project/message-switch,xapi-project/message-switch