Async GCS Mapper

Example:

import zarr
from gcs_aio_mapper import GCSMapperAio
from gcsfs import GCSMap
import logging

logging.basicConfig(level=logging.DEBUG)
n = 25

def build_gs_async():
    store = GCSMapperAio("gs://bucket/tmp/test.zarr", cache_size=n)
    g = zarr.open_array(store, shape=(n,), chunks=(3,), mode="w")
    for i in range(n):
        g[i] = i
    store.flush()


def build_gs():
    store = GCSMap("gs://bucket/tmp/test.zarr")
    g = zarr.open_array(store, shape=(n,), chunks=(3,), mode="w")
    for i in range(n):
        g[i] = i