Task: remove create/join methods
Task: remove create/join methods

Prepare for using the GstTaskPool object. We don't need the create and join
callbacks anymore, they will be handled by the pool.

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