tone_mapping: add pl_tone_map_params_infer

Resolving pl_tone_map_params at the time of pl_tone_map_generate is too late, because the latter can be generated dynamically based on the detected HDR peak, while we generally want to preserve a consistent 'look & feel' even when using HDR peak detection.

To fix this logic early on without duplicating logic, we need to expose the logic as a function that the tone mapping shader can call into.