BufferPrimitive: Add 'alpha' support

[donmccurdy]

Description

Work in progress.

Tasks:

• Expose collection.blendOption per-collection option
• Support pointMaterial.color.alpha
• Support pointMaterial.outlineColor.alpha
• Support polylineMaterial.color.alpha
• Support polygonMaterial.color.alpha

Issue number and link

n/a

Testing plan

TODO

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

AI acknowledgment

• I used AI to generate content in this PR
• If yes, I have reviewed the AI-generated content before submitting

If yes, I used the following Tools(s) and/or Service(s):

If yes, I used the following Model(s):

PR Dependency Tree

• PR BufferPrimitive: Add 'alpha' support #13384 👈

This tree was auto-generated by Charcoal

[github-actions]

Thank you for the pull request, @donmccurdy!

✅ We can confirm we have a CLA on file for you.