Add E2E failure notifications to Discord

[RobotSail]

We currently have integrations in place which send a message to our Slack channels whenever an E2E job fails. As part of our migration to Discord, we will want to update these to also update our Discord channels when a failure occurs.

The places where we need to update this are:

• https://github.com/instructlab/eval: feat: add discord e2e status reporting eval#200
• https://github.com/instructlab/instructlab: feat: add discord e2e status reporting instructlab#2821
• https://github.com/instructlab/training: feat: add discord e2e status reporting training#376
• https://github.com/instructlab/sdg: feat: add discord e2e status reporting sdg#455

[RobotSail]

We'd also need to update this: https://github.com/instructlab/instructlab/blob/92099a58869a416548240a4f3abaced5a0958937/docs/ci.md?plain=1#L95