Particle batching does not work in DX12.

Repro steps:
1. Open editor in DX12 mode (in command prompt "...\Unity.exe -allow-d3d12")
2. Switch the graphic API to DX12
3. Open any of the attached scenes and press play.
4. Observe batch count: particles are not batching.

Expected outcome: particles to batch.

Notes:
- not a regression, new code.
- occurs in both batch fix backports 5.4.0b10 (b83774801f70) and 5.3.3f1 (6f5aca424f44) (image and gif attached)
- 5.3 shows many visual artefacts and is unplayable. Issue is due to not having the latest graphics drivers.
- DX12 batches work decently in 5.1.0f3 (gif attached)