Support Mirax images

[ap--]

Draft while work in progress.

Recommended way for initial support is going the kerchunk route. If we provide the tiffslide properties in the zarrstore this format should already be supported.

Todo:

• [x] build minimal tiffslide properties and add to zattrs (see: tiffslide._kerchunk.to_kerchunk)
• [x] support per level positioning in composition
• [x] add missing position_record index types

If anyone has time to take this over, I'm happy to provide guidance :smiley: