Rename decoding buffers

New names align better with conventions. In particular, Buffer refers to
an owning type.

src/encoder/writer.rs

@@ -221,7 +221,7 @@ fn encoder_on_short_writes() {
     };
 
     let imgdata = vec![42u8; 100 * 100];
-    let mut data = crate::decoder::DecodingResult::U8(vec![]);
+    let mut data = crate::decoder::DecodingSampleBuffer::U8(vec![]);
 
     for comp in [
         super::Compression::Uncompressed,
@@ -247,7 +247,7 @@ fn encoder_on_short_writes() {
         let _layout = tiff_reader.read_image_to_buffer(&mut data).unwrap();
 
         assert!(
-            matches!(&data, crate::decoder::DecodingResult::U8(v) if *v == imgdata),
+            matches!(&data, crate::decoder::DecodingSampleBuffer::U8(v) if *v == imgdata),
             "{data:?} @ {}",
             data.as_buffer(0).byte_len()
         );