Add non_exhaustive compiler directive

Currently adding variants to enums is a breaking change. In an effort to
reduce the upgrade burden on users we can use the `non_exhaustive`
compiler directive so that adding a new variant does not cause
downstream code to break.

This is, however, a breaking change because downstream users will have
to add a wildcard match arm to any pattern matching code they have for
these enums.

Add `non_exhaustive` to the following tyes:

- `AddressType`
- `Payload`
- `LeafVersion`

src/util/address.rs

@@ -139,6 +139,7 @@ impl From<bech32::Error> for Error {
 
 /// The different types of addresses.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[non_exhaustive]
 pub enum AddressType {
     /// Pay to pubkey hash.
     P2pkh,
@@ -358,6 +359,7 @@ impl From<WitnessVersion> for opcodes::All {
 
 /// The method used to produce an address.
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[non_exhaustive]
 pub enum Payload {
     /// P2PKH address.
     PubkeyHash(PubkeyHash),

src/util/taproot.rs

@@ -870,6 +870,7 @@ impl fmt::UpperHex for FutureLeafVersion {
 
 /// The leaf version for tapleafs.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[non_exhaustive]
 pub enum LeafVersion {
     /// BIP-342 tapscript.
     TapScript,