[CDF-25284] 🤖 Agent test data (#1768)

# Description

I realized that we missed test data for Agents, found a few bugs:
1. We did no have `ignore_unknown_ids` set. 
2. We need to implement the `dump_resource` method to avoid redeploying
agents that are unchanged.

## Changelog

- [x] Patch
- [ ] Minor
- [ ] Skip

## cdf

### Fixed

- [alpha] When running `cdf deploy` with an `Agent` resource you no
longer get a `CogniteAPIError`.

## templates

No changes.
