iommufd/selftest: Test IOMMU_HWPT_GET_DIRTY_BITMAP

iommufd/selftest: Test IOMMU_HWPT_GET_DIRTY_BITMAP

Add a new test ioctl for simulating the dirty IOVAs in the mock domain, and
implement the mock iommu domain ops that get the dirty tracking supported.

The selftest exercises the usual main workflow of:

1) Setting dirty tracking from the iommu domain
2) Read and clear dirty IOPTEs

Different fixtures will test different IOVA range sizes, that exercise
corner cases of the bitmaps.

Link: https://lore.kernel.org/r/20231024135109.73787-17-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>