iommufd/selftest: Add domain_alloc_user() support in iommu mock

mainline inclusion
from mainline-v6.7-rc1
commit 408663619fcfc89c087df65b362c91bf0a0be617
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I8Y6AM
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?408663619fcfc89c087df65b362c91bf0a0be617

--------------------------------

Add mock_domain_alloc_user() and a new test case for
IOMMU_HWPT_ALLOC_NEST_PARENT.

Intel-SIG: 408663619fcf iommufd/selftest: Add domain_alloc_user() support in iommu mock
Backport IOMMUFD Dirty Tracking

Link: https://lore.kernel.org/r/20230928071528.26258-6-yi.l.liu@intel.com


Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
[ jz: amend commit log ]
Signed-off-by: Jason Zeng <jason.zeng@intel.com>