Reorder angles in RayPerceptionSensor

[RedTachyon]

Proposed change(s)

This PR changes the order in which rays are recorded in the RayPerceptionSensor. Currently, they start from the central ray, and then alternate between one to the left and one to the right. This makes it tricky to process these observations with a convolutional layer, which in my experience caused at least some people to reimplement a ray sensor instead of using the built-in one.

Useful links (Github issues, JIRA tickets, ML-Agents forum threads etc.)

Mentioned in Issue #5737

Types of change(s)

• Bug fix
• New feature
• Code refactor
• Breaking change
• Documentation update
• Other (please describe)

Checklist

• Added tests that prove my fix is effective or that my feature works
• Updated the changelog (if applicable)
• Updated the documentation (if applicable)
• Updated the migration guide (if applicable)

Other comments

[jrupert-unity]

The change makes sense but will have to happen with a means of maintaining backwards compatibility until we want to make a major version change since it would otherwise break existing models. This will be added to the backlog.

[jrupert-unity]

I hadn't noticed that the issue has already been logged. I'll follow up soon.