feat: allow ogmios url to be configured via env var.

[gilescope]

Description

Example usecase:

Allow running a partner chain's cli inside of docker. They may or may not be calling a command
that needs to use Ogmios. But if we can set up OGMIOS_URL=ws://host.docker.internal:1337 env var in the launch script then things will always work for them. (We could put various containers in a common network but it would be nice to have this option).

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• The size limit of 400 LOC isn't needlessly exceeded
• The PR refers to a JIRA ticket (if one exists)
• New tests are added if needed and existing tests are updated.
• New code is documented and existing documentation is updated.
• Relevant logging and metrics added
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff