Merge rust-bitcoin/rust-bitcoin#2388: Use hex-conservative to display pubkey

faa45cf10f Remove stale comment (Tobin C. Harding)
c82f26e960 Use hex-conservative to display pubkey (Tobin C. Harding)

Pull request description:

  We introduced `hex-conservative` ages ago, use it to display the `PublicKey`.

ACKs for top commit:
  Kixunil:
    ACK faa45cf10f
  apoelstra:
    ACK faa45cf10f

Tree-SHA512: 8ad14c7697314f8393ecb9a287215c505924d0655f7bf3536d4be83af983b142e06a96f802beb4548e2de051f1783549d8d1d1a8ebfb678f372a54010717752e

bitcoin/src/crypto/key.rs

@@ -220,12 +220,8 @@ pub struct SortKey(ArrayVec<u8, 65>);
 
 impl fmt::Display for PublicKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        // TODO: fast hex encoding
         self.with_serialized(|bytes| {
-            for ch in bytes {
-                write!(f, "{:02x}", ch)?;
-            }
-            Ok(())
+            fmt::Display::fmt(&bytes.as_hex(), f)
         })
     }
 }

bitcoin/src/pow.rs

@@ -832,7 +832,6 @@ impl crate::serde::Serialize for U256 {
         }
 
         if serializer.is_human_readable() {
-            // TODO: fast hex encoding.
             serializer.collect_str(&DisplayHex(*self))
         } else {
             let bytes = self.to_be_bytes();