drm/xe: Update PT layer with better error handling

Update PT layer so if a memory allocation for a PTE fails the error can
be propagated to the user without requiring the VM to be killed.

v5:
 - change return value invalidation_fence_init to void (Matthew Auld)
v7:
 - Invert i,j usage in two places (Matthew Auld)
 - s/0/NULL (Matthew Auld)
 - Don't ignore return value of xe_pt_new_shared (Matthew Auld)
 - Don't check for NULL in xe_pt_entry (Matthew Auld)
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240704041652.272920-7-matthew.brost@intel.com