Avoid KeyWitnessCount overestimation for delegation script credentials

Main idea is that we're taking the sum of
1. Key witness count needed for key credentials
2. Key witness count needed for (native) scripts

Unfortunately, this commit also breaks an integration test: #3830 (comment)
as `signTransaction` adds too many witnesses — or at least more than
what is needed and more than what we made room for when balancing. Next
commit will fix this by "making more room" by increasing the estimated
`KeyWitnessCount` in a more proper way.

lib/wallet/src/Cardano/Wallet/Shelley/Transaction.hs

@@ -1212,31 +1212,22 @@ estimateKeyWitnessCount utxo txbody@(Cardano.TxBody txbodycontent) =
 
     dummyKeyRole = Payment
 
-    apiScriptHashes =
-        let walletScripts = mapMaybe toTimelockScript scripts
-            toScriptHash =
-                Cardano.hashScript
-                . Cardano.SimpleScript
-                . toCardanoSimpleScript
-            toPair s = (s, toScriptHash s)
-        in toPair <$> walletScripts
-
-    estimateWitNumForCred = \case
-        Cardano.StakeCredentialByKey _ -> 1
-        Cardano.StakeCredentialByScript scriptHash ->
-            let pair = filter (\(_,sh) -> sh == scriptHash) apiScriptHashes
-            in case pair of
-                [(delScript,_)] ->
-                    estimateMaxWitnessRequiredPerInput delScript
-                _ -> error "there should be delegation script in the tx body"
 
+    estimateDelegSigningKeys :: Cardano.Certificate -> Integer
     estimateDelegSigningKeys = \case
         Cardano.StakeAddressRegistrationCertificate _ -> 0
         Cardano.StakeAddressDeregistrationCertificate cred ->
             estimateWitNumForCred cred
         Cardano.StakeAddressDelegationCertificate cred _ ->
             estimateWitNumForCred cred
         _ -> 1
+      where
+        -- Does not include the key witness needed for script credentials.
+        -- They are accounted for separately in @scriptVkWitsUpperBound@.
+        estimateWitNumForCred = \case
+            Cardano.StakeCredentialByKey _ -> 1
+            Cardano.StakeCredentialByScript _ -> 0
+
 
     toTimelockScript
         :: Ledger.Script (Cardano.ShelleyLedgerEra era)