class Bootsnap::LoadPathCache::LoadedFeaturesIndex

first purge and work from there.
If access patterns make this not-okay, we can lazy-invert the LFI on
We've optimized for initialize and register to be fast, and purge to be tolerable.

def purge(feature)
  @mutex.synchronize do
    feat_hash = feature.hash
    @lfi.reject! { |_, hash| hash == feat_hash }
  end
end