[MEDIA_PIPEINE_TF] Adap Bit Rate - position for max/min level

Hello,

I have made a proposal on the API to control when a level shall apply by adding position argument. This will help control the transition if for example different periods occur and one does not want to apply the new max level or min to the current period.

I also added to the adaptationSetChanged callback an indication of the position at which change in quality levels takes place. This will work in conjunction with the setting of max and minLevels.

Regards,
JanL