add: add batch storage RPC methods

[quantumshiro]

i fixed #32566

• Rationale:
  - Repeated calls to debug_getStorageAt for local simulations incur RPC round-trip overhead.
  - This PR adds batch variants to fetch multiple storage slots in one request, reducing latency and overhead.
  - This PR adds batch variants to fetch multiple storage slots in one request, reducing latency and overhead.

• New RPC Methods:
  - debug_batchGetStorageAt
  - Params: [address, [hexKey, ...], blockNrOrHash]
  - Returns: []hexbytes in the same order as input keys.

• debug_batchGetStorage
  - Params: [{ address: [hexKey, ...], ... }, blockNrOrHash]
  - Returns: { address: []hexbytes } with per-address order preserved.

• Implementation:
  - Location: internal/ethapi/api.go in DebugAPI.
  - Uses api.b.StateAndHeaderByNumberOrHash and state.GetState.
  - Key parsing via existing decodeHash.
  - Errors:
  - Invalid key format returns an error (whole request fails for minimal implementation).
  - Final state.Error() propagated.

• Example Usage:
  - Single address:
  - {"jsonrpc":"2.0","id":1,"method":"debug_batchGetStorageAt","params":["0xabc...",[ "0x0", "0x1" ],"latest"]}
  - Result: ["0x...32B","0x...32B"]

• Multiple addresses:
  - {"jsonrpc":"2.0","id":2,"method":"debug_batchGetStorage","params":[{"0xabc...":["0x0","0x1"],"0xdef...": ["0x2"]},"latest"]}
  - Result: {"0xabc...":["0x...","0x..."],"0xdef...":["0x..."]}

• Validation:
  - Built geth and verified RPC exposure with --dev --http.
  - Sample curl:
  - debug_batchGetStorageAt: curl -s -H 'Content-Type: application/json' --data '{"jsonrpc":"2.0","id":1,"method":"debug_batchGetStorageAt","params":["0x000...000",[ "0x0", "0x1" ],"latest"]}' http://127.0.0.1:18545
  - debug_batchGetStorage: curl -s -H 'Content-Type: application/json' --data '{"jsonrpc":"2.0","id":2,"method":"debug_batchGetStorage","params":[{"0x000...000":["0x0","0x1"]},"latest"]}' http://127.0.0.1:18545

[s1na]

Yeah I think only one of them suffices. Let's keep batchGetStorage since it's more general. I think it would be useful to query storage of multiple contracts.

Also please add some tests, I have a feeling it's vibe coded :)