Unreachable searchmap islands cause performance degradation

[lynxlynxlynx]

The bad news: When exhausting on a big map, the algorithm is simply expensive, all the observed frame drops are a result of unfortunate geometry/searchmap blocking. It is especially bad when the ignore-actors flag fails the second time with a full group, because there is actually just no path, see BG2 slums:

Yet there is a way (I can submit a PR if interested) to reuse a little bit of information to halve the penalty by skipping the ignore-actors run if there wasn't any actor to potentially bump into.

The T* stuff doesn't hurt r/n on small maps but on larger ones, we get what we see if there is no path to find. Not sure what to do about this at the moment.

Originally posted by @MarcelHB in #1692 (comment)

See the rest of the discussion there.