Kuba:
Introduced by the change from total physical memory to available memory used in GPU lightmapper's scheduling logic: https://ono.unity3d.com/unity/unity/pull-request/91177/_/graphics/gi/radeonrays/openclfreememory#comment-831463

[GPU PLM] Neverending bake in ArchViz project when Progressive Updates is on

Steps to repro:

1. Open the attached project and 'AVP6_Desktop' scene;
2. In the Lighting window enable the 'Progressive Updates' checkbox;
3. In the Lighting window press 'Generate Lighting' button.

Actual result:
Baking is stuck and never finishes. The ETA is jumping up and down constantly.

Expected result:
Baking completes successfully.

Notes:
- Reproducible in 2020.1.0a14;
- Not reproducible with 2019.3.0f4;
- Reproducible on Windows with NVIDIA GeForce RTX 2080;
- Reproducible only for the GPU Lightmapper.
- The issue seems to be introduced with the Progressive Updates feature for the GPU Lightmapper.
- Not reproducible when progressive updates are disabled.