Replace Tesla with Req

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

### AI Policy

- [x] I agree to follow this project's AI Policy, or I agree that AI was not used while creating this issue.

### Is your feature request related to a problem? Please describe.

We typically use Req across the Ash ecosystem rather than Tesla, so we want to align on a single HTTP client library.

### Describe the solution you'd like

As discussed in Ash Office Hours, Req now supports pipelines like Tesla does and this could be a decent upgrade.

### Describe alternatives you've considered

_No response_

### Additional context

_No response_