This utility was already duplicated in two places and planned to be used
more. While we should usually avoid creating arrays the size of the
indexed array (rather than the size of the mask), sometimes it does seem
to be the best option, and we're helped by the fact that most memory
stays unintialized for a small mask (allocating but not writing to memory
pages at all generally isn't too expensive).
Pull Request: https://projects.blender.org/blender/blender/pulls/115491
21a2390f4c