Move NetworkValidationError within file

Done in preparation for adding the `NetworkValidationError` as a variant
of `ParseError`.

Move the `NetworkValidationError` type to beneath `ParseError`.

Code move only, no other changes.

bitcoin/src/address/error.rs

@@ -9,26 +9,6 @@ use crate::blockdata::script::{witness_program, witness_version};
 use crate::prelude::*;
 use crate::Network;
 
-/// Address's network differs from required one.
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct NetworkValidationError {
-    /// Network that was required.
-    pub(crate) required: Network,
-    /// The address itself.
-    pub(crate) address: Address<NetworkUnchecked>,
-}
-
-impl fmt::Display for NetworkValidationError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "address ")?;
-        fmt::Display::fmt(&self.address.0, f)?;
-        write!(f, " is not valid on {}", self.required)
-    }
-}
-
-#[cfg(feature = "std")]
-impl std::error::Error for NetworkValidationError {}
-
 /// Error while generating address from script.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[non_exhaustive]
@@ -228,6 +208,26 @@ impl std::error::Error for UnknownHrpError {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
 }
 
+/// Address's network differs from required one.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct NetworkValidationError {
+    /// Network that was required.
+    pub(crate) required: Network,
+    /// The address itself.
+    pub(crate) address: Address<NetworkUnchecked>,
+}
+
+impl fmt::Display for NetworkValidationError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "address ")?;
+        fmt::Display::fmt(&self.address.0, f)?;
+        write!(f, " is not valid on {}", self.required)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for NetworkValidationError {}
+
 /// Decoded base58 data was an invalid length.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InvalidBase58PayloadLengthError {