shielded-pool(ics20): process truncated addresses in packet data (#4962)

## Describe your changes

This PR makes sure that truncated addresses are encoded correctly when
ICS20 withdrawals are marshaled into fungible packet data.

In addition to that, it modifies pcli to (hazardously?) handcraft a
return `Address` with an identity clue key and zero diversifier.

To test this PR, one can performa IBC roundtrip against a testnet chain
with broken bech32m handling (e.g, `grand-1`).

## Issue ticket number and link

#4950 

## Checklist before requesting a review

- [x] I have added guiding text to explain how a reviewer should test
these changes.

- [x] If this code contains consensus-breaking changes, I have added the
"consensus-breaking" label. Otherwise, I declare my belief that there
are not consensus-breaking changes, for the following reason:

  > CB release branch.

crates/bin/pcli/src/command/tx.rs

@@ -1023,10 +1023,18 @@ impl TxCmd {
             } => {
                 let destination_chain_address = to;
 
-                let (ephemeral_return_address, _) = app
-                    .config
-                    .full_viewing_key
-                    .ephemeral_address(OsRng, AddressIndex::from(*source));
+                let ephemeral_return_address = if *use_transparent_address {
+                    let ivk = app.config.full_viewing_key.incoming();
+
+                    ivk.transparent_address()
+                        .parse::<Address>()
+                        .expect("we round-trip from a valid transparent address")
+                } else {
+                    app.config
+                        .full_viewing_key
+                        .ephemeral_address(OsRng, AddressIndex::from(*source))
+                        .0
+                };
 
                 let timeout_height = match timeout_height {
                     Some(h) => h.clone(),

crates/core/component/shielded-pool/src/ics20_withdrawal.rs

@@ -167,9 +167,14 @@ impl TryFrom<pb::Ics20Withdrawal> for Ics20Withdrawal {
 
 impl From<Ics20Withdrawal> for pb::FungibleTokenPacketData {
     fn from(w: Ics20Withdrawal) -> Self {
-        let return_address = match w.use_compat_address {
-            true => w.return_address.compat_encoding(),
-            false => w.return_address.to_string(),
+        let ordinary_return_address = w.return_address.to_string();
+
+        let return_address = if w.use_transparent_address {
+            w.return_address
+                .encode_as_transparent_address()
+                .unwrap_or_else(|| ordinary_return_address)
+        } else {
+            ordinary_return_address
         };
 
         pb::FungibleTokenPacketData {

crates/core/transaction/src/view.rs

@@ -517,11 +517,14 @@ mod test {
 
     #[cfg(test)]
     fn dummy_spend() -> spend::Spend {
+        use penumbra_shielded_pool::EncryptedBackref;
+
         spend::Spend {
             body: spend::Body {
                 balance_commitment: dummy_commitment(),
                 nullifier: Nullifier(Fq::default()),
                 rk: dummy_pk(),
+                encrypted_backref: EncryptedBackref::dummy(),
             },
             auth_sig: dummy_sig(),
             proof: dummy_proof_spend(),