Invalidation for large relations

[pnorman]

Invalidation of tiles for large relations could lead to all the tiles in the US being invalidated by a tag change on a US border relation. It would be desirable to be able to not invalidate the interior of large boundary relations.

cc @gravitystorm

[lonvia]

cc @Nakaner

[pnorman]

A misdirected email from @woodpeck from 2013 said

Normally, expire_tiles_from_poly will expire tiles for the whole bounding box of the polygon unless the bbox has a width or height higher than EXPIRE_TILES_MAX_BBOX, in which case only those tiles actually touched by the outline of the polygon will be expired.

This should make sure that the whole of the US is never invalidated.

[joto]

Large multipolygon relations are handled through the --expire-bbox-size mechanism. For future ideas see #1662.