KVM backport for 9.4

Merge Request Required Information

Summary of Changes

This draft updates KVM to 6.6 and also includes the guestmem patches (initially destined to 6.7, but delayed to 6.8).

The unrecognized upstream CIDs are all from https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=next (particularly this topic branch).

Approved Development Ticket

All submissions to CentOS Stream must reference an approved ticket in Red Hat Jira. Please follow the CentOS Stream contribution documentation for how to file this ticket and have it approved.

JIRA: https://issues.redhat.com/browse/RHEL-14702

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>