drm/i915/debugfs: hook up ttm_resource_manager_debug

This should give a more complete view of the various bits of internal
resource manager state, for device local-memory.

v2(Thomas):
   - Move the region printing into a nice helper

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819093419.295636-2-matthew.auld@intel.com