The problem here was that `free_data_after_sync` frees the particle cache in headless or locked-UI mode, but the second view doesn't regenerate them.
For multi-view renders, dropping caches is a tradeoff between compute and memory - dropping allows to reduce peak memory usage, but requires recomputation for the next view. With the current design however, dropping is not something that is easily achievable anyways (see the referenced bugs). So until something more reliable and better fitting is implemented, keep the data from Blender side until the last view.
Since `free_data_after_sync` doesn't do anything for baking or viewport renders anyways, it's easiest to just move this out into `BlenderSession::render` since that already checks whether another view is still outstanding.
Also fixes#73221 and #107589.
Pull Request: https://projects.blender.org/blender/blender/pulls/120543
c9c777ddaa