Fix credits for request render mode

[lilleyse]

Reverts #7877 because of flickering credits in request render mode. Now I remember this was the exact reason why credit updates were moved back into the render pass in 43c0141.

Basically the globe only updates credits in the render pass, not its update pass, so any frames that are skipped by request render mode won't show the credits.

The fix now is to move the 3D Tiles credit update into update rather than postPassesUpdate so that 3D Tiles credits get added within the render pass.

Sancastle - this will show flickery credits in master but not this branch.

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ 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.