Read a DNG's NoiseProfile

The converter's measured noise for the body at that ISO, (S, O) per CFA
plane: the learned denoise's best source for a body with no table of its
own (denoise.md §3.3). Read from the header beside the colour tags, and
printed by rawinfo. Checked against tifffile on a 6D DNG at ISO 5000: all
six values agree.

core/dr-decode/examples/rawinfo.rs

@@ -32,6 +32,10 @@ fn main() {
     println!("black           {:?}", raw.black_level);
     println!("white           {}", raw.white_level);
     println!("wb_coeffs       {:?}", raw.wb_coeffs);
+    match dr_decode::noise_profile(&bytes) {
+        Some(p) => println!("noise profile   {p:?}   ((S, O) per plane)"),
+        None => println!("noise profile   none"),
+    }
 
     match raw.color_matrix {
         Some(m) => {