Add incident attributes

[adrielp]

Overview

Add incident attributes to semantic conventions.

This directly comes out of conversations for the initial CI/CD registry attributes. Discussion occurred and the decision was made to temporarily remove incident.yaml from the pull request & re-evaluate as a separate iteration pull request.

Resources:

• [cicd] add initial cicd attributes to registry #1075 (comment)
• Proposed Attribute Conventions for CI/CD #915 (comment)
• [cicd] add initial cicd attributes to registry #1075 (comment)

Notes:

• This likely should be under outage.incident instead of just incident at the root.
• Incidents can be related to CI/CD but can be related to other things too.