feat: support timed_ prefix for RPC method aliases

[krabat-l]

Summary

Add support for timed_ prefixed RPC method names. When a request uses a method like timed_debug_traceBlockByNumber, the server strips the prefix and routes it
to the same handler as debug_traceBlockByNumber.

Changes

• metrics.rs: Add TIMED_PREFIX, timed method name constants, TIMED_METHOD_ALIASES mapping, and strip_timed_prefix() helper. Updated
  record_rpc_request/record_rpc_error to strip the prefix so timed calls share the same metrics counters.
• rpc_service.rs: Register timed_ aliases via module.register_alias() in into_rpc_module().

Supported aliases

Alias	Routes to
timed_debug_traceBlockByNumber	debug_traceBlockByNumber
timed_debug_traceBlockByHash	debug_traceBlockByHash
timed_debug_traceTransaction	debug_traceTransaction
timed_debug_getCacheStatus	debug_getCacheStatus
timed_trace_block	trace_block
timed_trace_transaction	trace_transaction

Tests

Added 8 unit tests covering prefix stripping, alias consistency, alias registration on RpcModule, and duplicate rejection.