feat: Include the server request id in the error shown by Pavex CLI, if relevant

[LukeMathWalker]

https://api.pavex.dev will always populate the X-Server-Request-Id header whenever it returns a response. It looks like sri-xxxx, since it's built on ServerRequestId.
Pavex's CLI should include that request id whenever it exposes an error to the user that traces back to a failed request to the API. This allows the user to communicate that id back to us when triaging the issue, thus speeding up resolution.