bitcoin.py/transaction.py: API changes: rm most hex usage

Instead of some functions operating with hex strings,
and others using bytes, this consolidates most things to use bytes.

This mainly focuses on bitcoin.py and transaction.py,
and then adapts the API usages in other files.

Notably,
- scripts,
- pubkeys,
- signatures
should be bytes in almost all places now.

electrum/plugins/digitalbitbox/digitalbitbox.py

@@ -547,7 +547,7 @@ class DigitalBitbox_KeyStore(Hardware_KeyStore):
                 if not inputPath:
                     self.give_error("No matching pubkey for sign_transaction")  # should never happen
                 inputPath = convert_bip32_intpath_to_strpath(inputPath)
-                inputHash = sha256d(bfh(tx.serialize_preimage(i)))
+                inputHash = sha256d(tx.serialize_preimage(i))
                 hasharray_i = {'hash': to_hexstr(inputHash), 'keypath': inputPath}
                 hasharray.append(hasharray_i)
                 inputhasharray.append(inputHash)
@@ -659,8 +659,8 @@ class DigitalBitbox_KeyStore(Hardware_KeyStore):
                     sig_r = int(signed['sig'][:64], 16)
                     sig_s = int(signed['sig'][64:], 16)
                     sig = ecc.ecdsa_der_sig_from_r_and_s(sig_r, sig_s)
-                    sig = to_hexstr(sig) + Sighash.to_sigbytes(Sighash.ALL).hex()
-                    tx.add_signature_to_txin(txin_idx=i, signing_pubkey=pubkey_bytes.hex(), sig=sig)
+                    sig = sig + Sighash.to_sigbytes(Sighash.ALL)
+                    tx.add_signature_to_txin(txin_idx=i, signing_pubkey=pubkey_bytes, sig=sig)
         except UserCancelled:
             raise
         except BaseException as e: