Test roundtripping of Blosc codec to/from Kerchunk

[maxrjones]

@d-v-b pointed out that the Zarr V2/V3 codec metadata conversion extended in #713 and originally included in

VirtualiZarr/virtualizarr/codecs.py

Lines 23 to 32 in 572f3b7

	def numcodec_config_to_configurable(num_codec: dict) -> dict:
	"""
	Convert a numcodecs codec into a zarr v3 configurable.
	"""
	if num_codec["id"].startswith("numcodecs."):
	return num_codec
	num_codec_copy = num_codec.copy()
	name = "numcodecs." + num_codec_copy.pop("id")
	return {"name": name, "configuration": num_codec_copy}

may not work for Blosc because the v3 version of the blosc codec uses different values. We should test specifically for this case and special-case this compressor if needed.