Add arbitrary impl for ProprietaryKey and Key

cherry-pick of: caa4b91

Author: shinghim

bitcoin/src/psbt/raw.rs

@@ -8,6 +8,8 @@
 
 use core::fmt;
 
+#[cfg(feature = "arbitrary")]
+use actual_arbitrary::{self as arbitrary, Arbitrary, Unstructured};
 use io::{Read, Write};
 
 use super::serialize::{Deserialize, Serialize};
@@ -198,3 +200,21 @@ where
         Ok(deserialize(&key.key)?)
     }
 }
+
+#[cfg(feature = "arbitrary")]
+impl<'a> Arbitrary<'a> for ProprietaryKey {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(ProprietaryKey {
+            prefix: Vec::<u8>::arbitrary(u)?,
+            subtype: u8::arbitrary(u)?,
+            key: Vec::<u8>::arbitrary(u)?,
+        })
+    }
+}
+
+#[cfg(feature = "arbitrary")]
+impl<'a> Arbitrary<'a> for Key {
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        Ok(Key { type_value: u.arbitrary()?, key: Vec::<u8>::arbitrary(u)? })
+    }
+}