Auto merge of #141652 - compiler-errors:more-collect-and-apply, r=lqd

Rework `collect_and_apply` to not rely on size hint for optimization

I saw that we have quite a few `collect_and_apply` calls for N=3-7 (N=7 corresponding to cumulative 99% of nalgebra's calls). Didn't perf locally, but also this is super low-pri, so let's see what rust-timer says.

Author: bors