Terrain shaders aren't loaded in 2021.3 builds and above when loading asset bundles from 2019.3

How to reproduce:

1. Build a scene in 2019.3 into an asset bundle that uses default terrain shaders (i.e. values serialized under m_DetailBillboardShader, m_DetailMeshLitShader, m_DetailMeshGrassShader).
2. Load the bundle at runtime in a 2021.3 standalone player.
3. Observe the shaders were not loaded.

 

The issue is present in DetailDatabase where DetailDatabase::Transfer is not loading shaders serialized under the older m_DetailBillboardShader, m_DetailMeshLitShader, m_DetailMeshGrassShader properties.

 

DetailDatabase::Transfer's version was bumped to 4 in some 2022 branches so perhaps this'd now be supportable with a pre-version 4 serialization check?