Integrate #4018 calcDataSizeJ2C Adjust curve for more than 6 layers

[marchcat]

Description

See #4018.

[marchcat]

Reopen for testing.

[AtlasLinden]

Not seeing many "gray blobs" as per the PR (tested the SLB regions) however it will be good to have user feedback regarding this.
For now passing QA.
Verified on Second Life Project 7.1.14.15976006598 (GLTF Mesh Import) on Win11/MacOS