Feat: IoMmu protocol

[PelleKrab]

This PR adds the IoMmu Protocol to uefi-rs, enabling easy DMA (Direct Memory Access) for devices. This is a draft to get some initial feedback before writing uefi-rs tests. It is already working in my internal project. The main areas I would like feedback on are:

• Mapping and DMA Buffer Types: Is this too much abstraction? Should we simplify it by requiring the developer to manually call unmap() and free_buffer()?
• Should free_buffer_raw() and unmap_raw() be made public?
• Repository Organization: Is the general organization within the repo appropriate?

General Implementation:

// Allocate DMA buffer
let sz = some_buffer.len();
let page_num = bytes_to_pages(sz);
let mut host_buffer = iommu.allocate_buffer(
    MemoryType::BOOT_SERVICES_DATA,
    page_num,
    EdkiiIommuAttribute::MEMORY_CACHED,
)?;

// Map buffer for DMA
let (device_addr, mapping, wrt_size) = iommu.map(
    EdkiiIommuOperation::BUS_MASTER_COMMON_BUFFER,
    &host_buffer,
    size,
)?;

// Give permissions to the specified device 
iommu.set_attribute(some_device_handle, &mapping, EdkiiIommuAccess::READ)?;

// Copy firmware to DMA buffer
let dma_buf = host_buffer.deref_mut();
if sz > wrt_size {
    return Status::BUFFER_TOO_SMALL;
}
dma_buf[..sz].copy_from_slice(&some_buffer[..sz]);

// Notify the Device and pass the `device_addr`

ref:
#1723

[nicholasbishop]

Thanks for working on this :) I haven't had a chance to look at the uefi wrapper in detail yet, but overall it looks reasonable. Could you split the uefi-raw part out to a separate PR? That should be straightforward to review and merge in isolation.