constants: move mainnet/testnet/regtest-specific json files to chains/

note: I find "chains" less ambiguous than "networks" or "net".
Though the codebase already uses "net"/"network" for the same meaning,
e.g. see `electrum.constants.net` or the `getinfo` cmd dict containing a "network" key.. :/

electrum/constants.py

@@ -104,9 +104,9 @@ class BitcoinMainnet(AbstractNet):
     BOLT11_HRP = SEGWIT_HRP
     GENESIS = "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"
     DEFAULT_PORTS = {'t': '50001', 's': '50002'}
-    DEFAULT_SERVERS = read_json('servers.json', {})
-    FALLBACK_LN_NODES = create_fallback_node_list(read_json('fallback_lnnodes_mainnet.json', {}))
-    CHECKPOINTS = read_json('checkpoints.json', [])
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers.json'), {})
+    FALLBACK_LN_NODES = create_fallback_node_list(read_json(os.path.join('chains', 'fallback_lnnodes_mainnet.json'), {}))
+    CHECKPOINTS = read_json(os.path.join('chains', 'checkpoints.json'), [])
     BLOCK_HEIGHT_FIRST_LIGHTNING_CHANNELS = 497000
 
     XPRV_HEADERS = {
@@ -145,9 +145,9 @@ class BitcoinTestnet(AbstractNet):
     BOLT11_HRP = SEGWIT_HRP
     GENESIS = "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"
     DEFAULT_PORTS = {'t': '51001', 's': '51002'}
-    DEFAULT_SERVERS = read_json('servers_testnet.json', {})
-    FALLBACK_LN_NODES = create_fallback_node_list(read_json('fallback_lnnodes_testnet3.json', {}))
-    CHECKPOINTS = read_json('checkpoints_testnet.json', [])
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers_testnet.json'), {})
+    FALLBACK_LN_NODES = create_fallback_node_list(read_json(os.path.join('chains', 'fallback_lnnodes_testnet3.json'), {}))
+    CHECKPOINTS = read_json(os.path.join('chains', 'checkpoints_testnet.json'), [])
 
     XPRV_HEADERS = {
         'standard':    0x04358394,  # tprv
@@ -177,9 +177,9 @@ class BitcoinTestnet4(BitcoinTestnet):
 
     NET_NAME = "testnet4"
     GENESIS = "00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043"
-    DEFAULT_SERVERS = read_json('servers_testnet4.json', {})
-    FALLBACK_LN_NODES = create_fallback_node_list(read_json('fallback_lnnodes_testnet4.json', {}))
-    CHECKPOINTS = read_json('checkpoints_testnet4.json', [])
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers_testnet4.json'), {})
+    FALLBACK_LN_NODES = create_fallback_node_list(read_json(os.path.join('chains', 'fallback_lnnodes_testnet4.json'), {}))
+    CHECKPOINTS = read_json(os.path.join('chains', 'checkpoints_testnet4.json'), [])
     LN_DNS_SEEDS = []
 
 
@@ -189,7 +189,7 @@ class BitcoinRegtest(BitcoinTestnet):
     SEGWIT_HRP = "bcrt"
     BOLT11_HRP = SEGWIT_HRP
     GENESIS = "0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"
-    DEFAULT_SERVERS = read_json('servers_regtest.json', {})
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers_regtest.json'), {})
     FALLBACK_LN_NODES = []
     CHECKPOINTS = []
     LN_DNS_SEEDS = []
@@ -204,7 +204,7 @@ class BitcoinSimnet(BitcoinTestnet):
     SEGWIT_HRP = "sb"
     BOLT11_HRP = SEGWIT_HRP
     GENESIS = "683e86bd5c6d110d91b94b97137ba6bfe02dbbdb8e3dff722a669b5d69d77af6"
-    DEFAULT_SERVERS = read_json('servers_regtest.json', {})
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers_regtest.json'), {})
     FALLBACK_LN_NODES = []
     CHECKPOINTS = []
     LN_DNS_SEEDS = []
@@ -215,8 +215,8 @@ class BitcoinSignet(BitcoinTestnet):
     NET_NAME = "signet"
     BOLT11_HRP = "tbs"
     GENESIS = "00000008819873e925422c1ff0f99f7cc9bbb232af63a077a480a3633bee1ef6"
-    DEFAULT_SERVERS = read_json('servers_signet.json', {})
-    FALLBACK_LN_NODES = create_fallback_node_list(read_json('fallback_lnnodes_signet.json', {}))
+    DEFAULT_SERVERS = read_json(os.path.join('chains', 'servers_signet.json'), {})
+    FALLBACK_LN_NODES = create_fallback_node_list(read_json(os.path.join('chains', 'fallback_lnnodes_signet.json'), {}))
     CHECKPOINTS = []
     LN_DNS_SEEDS = []