network_parameters: change bip21 schema liquidtestnet->liquidnetwork

the schema doesn't need to convey the network, indeed for bitcoin we
have only `bitcoin:` as schema for every network (mainnet, testnet,
signet, regtest)

This is indeed a breaking change and the liquidtesnet schema is used in
the wild, however, since it's breaking only for testnet networks, it
makes sense to change it.

Author: RCasatta

docs/source/examples/get_networks.json

@@ -220,7 +220,7 @@
       "asset_registry_onion_url": "http://lhquhzzpzg5tyymcqep24fynpzzqqg3m3rlh7ascnw5cpqsro35bfxyd.onion/testnet/",
       "asset_registry_url": "https://assets-testnet.blockstream.info/",
       "bech32_prefix": "tex",
-      "bip21_prefix": "liquidtestnet",
+      "bip21_prefix": "liquidnetwork",
       "blech32_prefix": "tlq",
       "blinded_prefix": 23,
       "blob_server_onion_url": "",
@@ -480,7 +480,7 @@
       "asset_registry_onion_url": "http://lhquhzzpzg5tyymcqep24fynpzzqqg3m3rlh7ascnw5cpqsro35bfxyd.onion/testnet/",
       "asset_registry_url": "https://assets-testnet.blockstream.info/",
       "bech32_prefix": "tex",
-      "bip21_prefix": "liquidtestnet",
+      "bip21_prefix": "liquidnetwork",
       "blech32_prefix": "tlq",
       "blinded_prefix": 23,
       "blob_server_onion_url": "",

src/network_parameters.cpp

@@ -329,7 +329,7 @@ static std::map<std::string, std::shared_ptr<nlohmann::json>> registered_network
             { "asset_registry_url", "https://assets-testnet.blockstream.info/" },
             { "asset_registry_onion_url", "http://lhquhzzpzg5tyymcqep24fynpzzqqg3m3rlh7ascnw5cpqsro35bfxyd.onion/testnet/" },
             { "bech32_prefix", "tex" },
-            { "bip21_prefix", "liquidtestnet" },
+            { "bip21_prefix", "liquidnetwork" },
             { "blech32_prefix", "tlq" },
             { "blinded_prefix", 23u },
             { "blob_server_url", std::string() },
@@ -713,7 +713,7 @@ static std::map<std::string, std::shared_ptr<nlohmann::json>> registered_network
             { "asset_registry_url", "https://assets-testnet.blockstream.info/" },
             { "asset_registry_onion_url", "http://lhquhzzpzg5tyymcqep24fynpzzqqg3m3rlh7ascnw5cpqsro35bfxyd.onion/testnet/" },
             { "bech32_prefix", "tex" },
-            { "bip21_prefix", "liquidtestnet" },
+            { "bip21_prefix", "liquidnetwork" },
             { "blech32_prefix", "tlq" },
             { "blinded_prefix", 23u },
             { "blob_server_url", std::string() },