Remove `map` infix in lemmas about `dom` and `filter`.

The combination of dom and filter only makes sense for maps, so the map infix is useless. Other similar lemmas do not have such an infix either, so it's also inconsistent.

Rename dom_map filter → dom_filter, dom_map_filter_L → dom_filter_L, and dom_map_filter_subseteq → dom_filter_subseteq.

This was pointed out by @atrieu in !175 (comment 53746)