Reproduces on: 2021.3.43f1, 2022.3.46f1, 6000.0.19f1

The layer lit shader has an issue with the layer addition in case of a copy.

steps to reproduce:

1. Launch the latest Unity version with {}HDRP{}.
2. Use linked package or create a new scene with an object using the layer lit shader with 3 layers.
3. Make sure all 3 layers have materials assigned to them
4. Do a copy of the material with 3 layers.
5. In the material copy, add a 4th layer.
6. In the layer material list the 4th layer is not visible and doesn't work when the material in assigned to an ibject.

[https://docs.unity3d.com/Packages/com.unity.render-pipelines.high-definition@12.0/manual/Layered-Lit-Shader.html]

Actual result:  The added layer is not referenced in the material list and has no effect in the scene/game view.
Expected result: The layer addition should work even on a material copy.

Reproduced on: PC with Windows 10.