Make AsyncArray.nchunks_initialized async#2449

d-v-b merged 3 commits intozarr-developers:mainzarr-developers/zarr-python:mainfrom

TomAugspurger:tom/fix/async-nchunks-initializedTomAugspurger/zarr-python:tom/fix/async-nchunks-initializedCopy head branch name to clipboard