drm/i915/display: add intel_display_snapshot abstraction

drm/i915/display: add intel_display_snapshot abstraction

The error state capture still handles display info at a too detailed
level. Start abstracting the whole display snapshot capture and printing
at a higher level. Move overlay to display snapshot first.

Use the same nomenclature and style as in xe devcoredump, in preparation
for perhaps some day bolting the snapshots there as well.

v3: Fix build harder for CONFIG_DRM_I915_CAPTURE_ERROR=n

v2: Fix build for CONFIG_DRM_I915_CAPTURE_ERROR=n (kernel test robot)

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ba6a36759600c2d35405c41a0fc9d69f676df77d.1726151571.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>