added force PPL checkbox
Partially resolves Feature #7271
Added a checkbox to the Lighting tab for "force per-pixel lighting". Also logic for loading and saving this setting.
This option can be necessary on Apple Silicon to correct visual issues, and access from the UI should improve experience for Mac users.
Tested on MBP M3 macOS 14.3, manual testing to ensure option appeared and reflected actual setting, as well as updated on toggle.