Refactor sync time verification

Instead of verifying txs at sync time in every backend, its moved to
script_sync to by default be available to any backend.

src/blockchain/electrum.rs

@@ -190,19 +190,6 @@ impl Blockchain for ElectrumBlockchain {
                                         .output
                                         .get(input.previous_output.vout as usize)
                                         .ok_or_else(electrum_goof)?;
-                                    // Verify this input if requested via feature flag
-                                    #[cfg(feature = "verify")]
-                                    {
-                                        use crate::wallet::verify::VerifyError;
-                                        let serialized_tx = bitcoin::consensus::serialize(&tx);
-                                        bitcoinconsensus::verify(
-                                            txout.script_pubkey.to_bytes().as_ref(),
-                                            txout.value,
-                                            &serialized_tx,
-                                            input_index,
-                                        )
-                                        .map_err(|e| VerifyError::from(e))?;
-                                    }
                                     input_index += 1;
                                     Ok(Some(txout.clone()))
                                 })