tx-psbt: pass in the witness script (if known) when adding an input

Update the `bitcoin_tx_add_input` interface to accept a witness script
and or scriptPubkey.

We save the amount + witness script + witness program (if known) to
the PSBT object for a transaction when creating an input.

common/initial_commit_tx.h

@@ -76,6 +76,7 @@ static inline struct amount_sat commit_tx_base_fee(u32 feerate_per_kw,
  * initial_commit_tx: create (unsigned) commitment tx to spend the funding tx output
  * @ctx: context to allocate transaction and @htlc_map from.
  * @funding_txid, @funding_out, @funding: funding outpoint.
+ * @funding_wscript: scriptPubkey of the funding output
  * @opener: is the LOCAL or REMOTE paying the fee?
  * @keyset: keys derived for this commit tx.
  * @feerate_per_kw: feerate to use
@@ -96,6 +97,7 @@ struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
 				     const struct bitcoin_txid *funding_txid,
 				     unsigned int funding_txout,
 				     struct amount_sat funding,
+				     u8 *funding_wscript,
 				     enum side opener,
 				     u16 to_self_delay,
 				     const struct keyset *keyset,