Part 5 - jsonrpc: replace jsonrpcserver/jsonrpcclient with custom implementation

[ping-ke]

Summary

jsonrpcserver 3.x and jsonrpcclient 2.x are no longer maintained
and are incompatible with Python 3.13.

• Add quarkchain/cluster/jsonrpcserver.py: a lightweight JSON-RPC 2.0
  server dispatcher built on aiohttp (RpcMethods, JsonRpcError hierarchy,
  positional and named parameter dispatch)
• Add quarkchain/jsonrpc_client.py: JsonRpcClient (synchronous, httpx-based)
  and AsyncJsonRpcClient (async, aiohttp-based) replacing the old clients
• Update jsonrpc.py to use the new RpcMethods class and make
  start_*_server() classmethods async
• Replace jsonrpcclient calls in all tools and prom.py with JsonRpcClient.call()
• Rename quarkchain/tools/stats → quarkchain/tools/stats.py (was missing extension)
• Update test_jsonrpc.py to use AsyncJsonRpcClient

Test plan

• pytest quarkchain/cluster/tests/test_jsonrpc.py passes
• Public and private JSON-RPC endpoints respond correctly
• external_miner.py can fetch work and submit results

[qzhodl]

Code review

Found 2 issues:

1. Typo: client.client() instead of client.call() in stats.py -- basic() calls client.client("getStats") but JsonRpcClient.client is the internal httpx.Client instance, not a callable RPC method. This will raise TypeError at runtime. The stats() function on line 35 correctly uses client.call("getStats").

pyquarkchain/quarkchain/tools/stats.py

Lines 20 to 22 in f867cb3

	def basic(client: JsonRpcClient, ip):
	s = client.client("getStats")
	msg = "QuarkChain Cluster Stats\n\n"

2. asyncio.get_running_loop() called from synchronous __init__ -- Both JSONRPCHttpServer.__init__ (line 509) and JSONRPCWebsocketServer.__init__ (line 1462) call asyncio.get_running_loop(). These constructors are invoked from synchronous main() in master.py and slave.py before the event loop is running, which will raise RuntimeError: no running event loop. The previous asyncio.get_event_loop() works in both sync and async contexts.

pyquarkchain/quarkchain/cluster/jsonrpc.py

Lines 505 to 510 in f867cb3

	def __init__(
	self, env, master_server: MasterServer, port, host, methods: RpcMethods
	):
	self.loop = asyncio.get_running_loop()
	self.port = port

pyquarkchain/quarkchain/cluster/jsonrpc.py

Lines 1458 to 1463 in f867cb3

	def __init__(
	self, env, slave_server: SlaveServer, port, host, methods: RpcMethods
	):
	self.loop = asyncio.get_running_loop()
	self.port = port

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