Preparatory patches for TDX support in KVM

Merge Request Required Information

Summary of Changes

Backport more patches, mostly from 6.12, that are needed to enable TDX support in KVM. These prerequisites are less self contained, but are enough to have a mostly conflict-free TDX backport.

Approved Development Ticket(s)

All submissions to CentOS Stream must reference a ticket in Red Hat Jira.

JIRA: https://issues.redhat.com/browse/RHEL-71541
Depends: https://issues.redhat.com/browse/RHEL-64444
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Omitted-fix: 3f749befb0998472470d850b11b430477c0718cc (irrelevant series of changes for odd Kconfigs)
Omitted-fix: ea4290d77bda2bd1f173a86f07aa79b568e0a6f8 (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 2a5fe5a01668e831af1de3951718fbf88b9a9b9c (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 338b655a1178900ac05aca7ac66dc28b05100430 (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 341e4023032fba6c02326bfc6babd63ef4039712 (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 1331343af6f502aecd274d522dd34bf7c965f484 (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 9ee62c33c0fe017ee02501a877f6f562363122fa (irrelevant series of changes for odd Kconfigs)
Omitted-fix: 2a5fe5a01668e831af1de3951718fbf88b9a9b9c (irrelevant series of changes for odd Kconfigs)
Omitted-fix: d822ca29a4fc5278fb511790dace44836e8cc40d (can be backported via perf)
Omitted-fix: 979956bc681105f34642971448c4cda048954a07 (irrelevant with RHEL gcc)
Omitted-fix: e120829dbf927c8b93cd5e06acfec0332cc82e02 (can be backported via perf)