Add helpers to safely add and delete the exec queues attached to a hw
engine group, and make use them at the time of creation and destruction of
the exec queues. Keeping track of them is required to control the
execution mode of the hw engine group.

v2: Improve error handling and robustness, suspend exec queues created in
    fault mode if group in dma-fence mode, init queue link (Matt Brost)

v3: Delete queue from hw engine group when it is destroyed by the user,
    also clean up at the time of closing the file in case the user did
    not destroy the queue

v4: Use correct list when checking if empty, do not add the queue if VM
    is in xe_vm_in_preempt_fence_mode (Matt Brost)

v5: Remove unrelated newline, add checks and asserts for group, unwind on
    suspend failure (Matt Brost)
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240809155156.1955925-4-francois.dugast@intel.com