HCF to manage the durable object storage and don't hard-code the URL and secret

[cdunster]

The Unyt Chain Transaction scenario currently uses a Durable Object storage hosted on Cloudflare under the Unyt organisation. We instead want to manage this storage under the Holochain Foundation account. Also, the URL and "secret" are currently hard-coded as plain text in the scenario, these must be moved to use the Nomad secret store and then the Nomad job needs to use the secret block in the run scenario job to get the URL and DO store secret.

There must also be a way of running the scenario locally and therefore the storage must have an option for hosting locally. This is possible with Cloudflare's Durable Object storage, see: https://developers.cloudflare.com/durable-objects/get-started/#6-develop-a-durable-object-worker-locally this should be easily supported locally, possible with a script or something to start it and set the required environment variables.

AC:

• A Durable Object store is hosted on Cloudflare under the HCF account
• Use Nomad secrets to configure the Unyt scenario (the secret can just be exposed to all scenarios though for ease)
• Can still run the scenario locally
• URL and secret are is no longer exposed