Create the async array explicitly in icechunk

[abarciauskas-bgse]

with create_array we are trying to fit a single abstraction over v2 and v3 arrays, and as a result create_array has a signature that doesn't look exactly like v2 or v3 array metadata. If you already have codecs, then it might make sense to create the asyncarray explicitly, by first creating a metadata document and then providing the rest of the arguments. would that work in your case?

Originally posted by @d-v-b in #2848