Read contract addresses from deployments.json

> `parse_deployment_output` gets the contract addresses from the output text. I think a better approach would be to read them from `deployments.json`.

_Originally posted by @wjmelements in [#41](https://github.com/FilOzone/foc-devnet/issues/41#issuecomment-3780839623)_

The deployment scripts modify deployments.json, setting addresses for the deployed contracts. It would be simpler to extract the devnet addresses from that.

See https://github.com/FilOzone/filecoin-services/issues/354 and https://github.com/FilOzone/filecoin-services/pull/364