Electrum integration tests fixes (#3702)

There are two fixes around Electrum integration tests. 
The first one is replacing the existing testing Falcrum server URL with
an operational one. The old one stopped working.
The second fix is around btc tx hashes for a given wallet. Integration
tests started reporting failures around mismatched expected vs actual
txs for the integration test wallet. It turned out that there was still
some movement in the wallet that was used for integration
tests and the latest txs were different. Here we picked a wallet that is
quite old and it seems that there is no more new movement. URL for the
btc address along with txs:
https://blockstream.info/address/bc1qrw5tn47ea05seyetlywltrdk06rldpk746etc9

internal/testdata/bitcoin/transaction.go

@@ -290,13 +290,13 @@ var TransactionsForPublicKeyHash = map[bitcoin.Network]struct {
 		},
 	},
 	bitcoin.Mainnet: {
-		PublicKeyHash: decodeString("b0ba76edfe18e81365bddd1d46511a57a4ff8dce"),
+		PublicKeyHash: decodeString("1ba8b9d7d9ebe90c932bf91df58db67e87f686de"),
 		Transactions: []bitcoin.Hash{
-			hashFromString("ea0b6862d4934e9910cb74984093267989bab7c61d508337bbb976165eb22553"),
-			hashFromString("78304889f2363d546dfe4af788e405464dd67fc1a057d7a6d45a8cf617f5f773"),
-			hashFromString("c11feea0f8b9e256e0a70ad58f88c7e3800d8ffbfb85edf7169629584a97a7ab"),
-			hashFromString("5cebf53de9cfde661e1193faf540727d4619399a289283e7b009f6953e49e769"),
-			hashFromString("4be52bc1873bcc9a3195d4075161cf686ba3856977cedd2fc43f13491755ff59"),
+			hashFromString("dbb67639fd5c2a6a1b2c7ea8e40bd392173e0a79563f4b2a6f5f514959f232eb"),
+			hashFromString("ae58884be48e1dc853ef31223b082e3edae1a49ccae1394406a318a7f8502f65"),
+			hashFromString("568e2bcad771b45f8a6851b8e9a4f65faaf56e9781cf07af73f4403697394909"),
+			hashFromString("7501fecc2584ac5aa7a67979098ecf8c46a6e9caf49b1ff0b228f89a45fe5d3a"),
+			hashFromString("58469686da18953e52d8f033b217890416a173a4da5df04b52d29e8feb55850d"),
 		},
 	},
 }

pkg/bitcoin/electrum/electrum_integration_test.go

@@ -64,7 +64,7 @@ var testConfigs = map[string]testConfig{
 	},
 	"fulcrum tcp": {
 		clientConfig: electrum.Config{
-			URL:                 "tcp://blackie.c3-soft.com:57005",
+			URL:                 "tcp://v22019051929289916.bestsrv.de:50001",
 			RequestTimeout:      requestTimeout * 2,
 			RequestRetryTimeout: requestRetryTimeout * 2,
 		},