basetransform: reevaluate proxy_alloc when reconfigured
basetransform: reevaluate proxy_alloc when reconfigured

When we reconfigure the transform element, make sure we reevaluate the proxying
of buffer_alloc the next time around.

Fixes #621332

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