[EngSys] Instruct copilot to ignore the PR templates (or add one specific to copilot)

Copilot is wasting time, and generating a worse PR summary, by looking at our PR templates. Can we tell it to either ignore the templates, or add a new bare-bones template specific to copilot?

```
Found 3 PR template(s): .github/PULL_REQUEST_TEMPLATE/control_plane_template.md, .github/PULL_REQUEST_TEMPLATE/data_plane_template.md, .github/PULL_REQUEST_TEMPLATE/sdk_configuration_template.md
git rev-parse HEAD
b7b12aab2647ae9500d6b16a963738888a51a024

copilot: Let me look at the available templates to determine which one best fits the problem statement about bumping simple-git dependency versions.
```

https://github.com/Azure/azure-rest-api-specs/actions/runs/22984528001/job/66731424888#step:28:1732