Resources plugin

# Summary

Today - the resources template has two downsides:

* It is expensive as it requires one pod per resource.
* It only supports a single resource.
* Resource manifests must come from the workflow.
* Resources are strings, not structured YAML

It would also be an opportunity to complete this:

* #7725
* #7179
* #7143
* #6862

I propose a new plugin:

```yaml
plugins:
resources:
- manifest:
value:
valueFrom:
url: ...
wait:
for: condition=Ready
status:
phase: Running
```

---

**Message from the maintainers**:

Love this enhancement proposal? Give it a 👍. We prioritise the proposals with the most 👍.

Start by reviewing the existing resources template and the linked issues #7725, #7179, #7143, and #6862. Compare the proposed YAML shape with the current limitations; done should cover multiple structured manifests, value or valueFrom inputs, and the proposed wait conditions.

Written by the indexing model from the issue text.