docs: improve --pmode documentation, the feature is fully functional
api: allow --psy-rdoq values up to 50; it can be beneficial for film grain
encoder: give more warnings when features are automatically disabled

and add comments describing why the combinations are prevented.  Some of them
are simply impossible, the option would have no affect and so it is best not to
pretend it is enabled. Some will not be useful (have a negative impact on
performance with no compression improvement). And others are just currently
broken and not typically used.
encoder: emit an Active Parameter Sets SEI in stream headers if interlaced

The APS is technically required if we're going to be emitting picture timing SEI
which we do for HRD and for interlaced inputs. The lack of APS for interlaced
content was causing a warning from the HM decoder and on Windows the decoder
would later crash.
Save intra mode in lowres