Added release function to PoolVector::Access.

For clarity, assign-to-release idiom for PoolVector::Read/Write
replaced with a function call.
Existing uses replaced (or removed if already handled by scope)

modules/tinyexr/image_loader_tinyexr.cpp

@@ -235,7 +235,7 @@ Error ImageLoaderTinyEXR::load_image(Ref<Image> p_image, FileAccess *f, bool p_f
 
 	p_image->create(exr_image.width, exr_image.height, false, format, imgdata);
 
-	w = PoolVector<uint8_t>::Write();
+	w.release();
 
 	FreeEXRHeader(&exr_header);
 	FreeEXRImage(&exr_image);