ggml : improve RPC tensor transfer logs (#30481)
- add rpc_log_format_size() and print byte counts in KiB/MiB/GiB across the
RPC client, server and transport traces
- add rpc_log_format_tensor() and include tensor name, op, type and shape in
the set/get/memset/copy/init tensor logs
- fix rpc_cmd_name() returning UNKNOWN for SET_TENSOR_2D, GET_TENSOR_2D,
COMM_INIT, COMM_ALLREDUCE and COMM_FREE
- move the log helpers to ggml-rpc/log.{h,cpp} under a common rpc_log_ prefix
Assisted-by: pi:llama.cpp/Qwen3.8-Flash-Next
