drm/xe/hw_engine_group: Introduce xe_hw_engine_group

A xe_hw_engine_group is a group of hw engines. Two hw engines belong to
the same xe_hw_engine_group if one hw engine cannot make progress while
the other is stuck on a page fault.

Typically, hw engines of the same group share some resources such as EUs,
but this really depends on the hardware configuration of the platforms.
The simple engines partitioning proposed here might be too conservative
but is intended to work for existing platforms. It can be optimized later
if more sets of independent engines are identified.

The hw engine groups are intended to be used in the context of faulting
long-running jobs submissions.

v2: Move to own files, improve error handling (Matt Brost)

v3: Fix build issue reported by CI, improve commit message (Matt Roper)

v4: Fix kernel doc

v5: Add switch case for XE_ENGINE_CLASS_OTHER

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/20240809155156.1955925-2-francois.dugast@intel.com