feat(ethereum): add provider cost metrics and update benchmarking report

[isSerge]

Update Ethereum benchmarks to calculate CU costs for each RPC request (according to Alchemy CU scheme) so we can clearly differentiate between expensive and cheap RPC calls (currently debug_traceTransaction and eth_getBlockByNumber look the same).

New benchmark report looks like this (against eRPC):

2026-07-30T10:29:19.876532Z  INFO Catchup Benchmark Report
catchup_completed: 100 blocks in 0.14s
  blocks_per_sec  693.3
  rpc_per_sec    762.7  (http_per_sec 62.4)
  total_rpc      110  (total_http 9)
  total_cu       2560  (cu_per_sec 17749.6  cu_per_block 25.6)
  total_tput_cu  2560  (tput_cu_per_sec 17749.6)
  batch_fetch_ms 125
  refetch_ms     0
  process_ms     19
  rpc_breakdown (logical, http round-trips, compute CU):
  eth_getBlockByNumber(Finalized)           1 (1 http)  cu 20
  eth_getBlockByNumber(batch)             100 (4 http)  cu 2000
  eth_getLogs(batch)                        9 (4 http)  cu 540