Auto merge of rust-lang#54318 - nnethercote:use-HybridBitSet-in-SparseBitMatrix, r=pnkfelix

Use `HybridBitSet` in `SparseBitMatrix`.

This fixes most of the remaining NLL memory regression.

r? @pnkfelix, because you reviewed rust-lang#54286.
cc @nikomatsakis, because NLL
cc @Mark-Simulacrum, because this removes `array_vec.rs`
cc @lqd, because this massively improves `unic-ucd-name`, and probably other public crates

Author: bors