Revert separate primitive framebuffer

[lilleyse]

Fixes #8366 and #8356

Reverts #8205. I'm going to open a separate next-release issue to add back this fix but address the depth plane problem #8356 (comment):

The points on the opposite side of the globe are rendered in the last frustum which is past the depth plane. The same thing happened in 1.62 but the points would get overwritten by globe commands in closer frustums.

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[mramato]

Please include a testing strategy or at least a bullet point reminding us of the need for a testing strategy so that this doesn't happen again.