model: consider removing agent.name

The name here should basically match the name of the crate that produced the image. I commented on this early. The `name` field of the `Agent` model is poorly conceived. I thought of it as a name for the program, e.g.
- ecs-test-agent
- sonobuoy-test-agent
- migration-test-agent
- eks-resource-agent

I don't think we are using it for anything at all and we should probably remove it from the model since it's a source of confusion that adds no value.

_Originally posted by @webern in https://github.com/bottlerocket-os/bottlerocket-test-system/pull/297#discussion_r808572177_

Start by locating the Agent model and searching the repository for uses of its name field. Confirm whether the field is unused, then update the affected model references and tests; done means the Agent model no longer exposes name and the test suite passes.

Written by the indexing model from the issue text.