basetransform: Allow the subclass to add new fields to caps when getting new caps from downstream
basetransform: Allow the subclass to add new fields to caps when getting new caps from downstream

This was already done in all other cases where new caps are handled
except upstream negotiation.

krichter722/gstreamer,jpakkane/gstreamer,Lachann/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,mrchapp/gstreamer,mrchapp/gstreamer,ylatuya/gstreamer,mparis/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,lovebug356/gstreamer,drothlis/gstreamer,centricular/gstreamer,drothlis/gstreamer,Distrotech/gstreamer,magcius/gstreamer,lovebug356/gstreamer,Lachann/gstreamer,drothlis/gstreamer,shelsonjava/gstreamer,justinjoy/gstreamer,ensonic/gstreamer,jpxiong/gstreamer,Lachann/gstreamer,ahmedammar/platform_external_gst_gstreamer,ensonic/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,magcius/gstreamer,surround-io/gstreamer,mrchapp/gstreamer,StreamUtils/gstreamer,magcius/gstreamer,collects/gstreamer,krieger-od/gstreamer,krieger-od/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,Distrotech/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,krieger-od/gstreamer,lubosz/gstreamer,magcius/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,ylatuya/gstreamer,krichter722/gstreamer,Distrotech/gstreamer,centricular/gstreamer,ensonic/gstreamer,krichter722/gstreamer,lovebug356/gstreamer,mparis/gstreamer,cfoch/gstreamer,cablelabs/gstreamer,Distrotech/gstreamer,lubosz/gstreamer,justinjoy/gstreamer,drothlis/gstreamer,shelsonjava/gstreamer,cfoch/gstreamer,mrchapp/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,centricular/gstreamer,jpakkane/gstreamer,ylatuya/gstreamer,cfoch/gstreamer,collects/gstreamer,lubosz/gstreamer,ahmedammar/platform_external_gst_gstreamer,justinjoy/gstreamer,drothlis/gstreamer,ensonic/gstreamer,jpakkane/gstreamer,ylatuya/gstreamer,ahmedammar/platform_external_gst_gstreamer,krieger-od/gstreamer,mrchapp/gstreamer,shelsonjava/gstreamer,surround-io/gstreamer,cfoch/gstreamer,cfoch/gstreamer,cablelabs/gstreamer,jpxiong/gstreamer,cablelabs/gstreamer,ahmedammar/platform_external_gst_gstreamer,ylatuya/gstreamer,justinjoy/gstreamer,ahmedammar/platform_external_gst_gstreamer,lovebug356/gstreamer,Lachann/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,centricular/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,mparis/gstreamer,collects/gstreamer,cablelabs/gstreamer,jpxiong/gstreamer,collects/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,Lachann/gstreamer,Distrotech/gstreamer,lovebug356/gstreamer,magcius/gstreamer,collects/gstreamer,mparis/gstreamer,krieger-od/gstreamer