Support utilizationRatio

[Cafe137]

This new field made it into the postage batch response schema, so we no longer need to calculate the utilization ratio on the client side.

We should keep an Utils function that lets developers do this calculation, but this can simplify our SDK glue code.

Relevant change in Bee:

ethersphere/bee@91888e9#diff-009e52248dc5b40de2151d92acae31f35efc22c10d2584952e07d9833e37684aR543-R552

Relevant part is Bee-JS:

https://github.com/ethersphere/bee-js/blob/master/src/utils/stamps.ts#L224

[slapec93]

v2.8.0 (latest stable) doesn't contain this change to have it in bee-js, we need to have a fallback logic