common : reimplement logging (#9418)

https://github.com/ggerganov/llama.cpp/pull/9418

examples/server/bench/README.md

@@ -40,7 +40,6 @@ server --host localhost --port 8080 \
   --parallel 8 \
   --batch-size 512 \
   --ctx-size 4096 \
-  --log-format text \
   -ngl 33
 ```
 

examples/server/bench/bench.py

@@ -272,7 +272,6 @@ def start_server_background(args):
     server_args.append('--cont-batching')
     server_args.append('--metrics')
     server_args.append('--flash-attn')
-    server_args.extend(['--log-format', "text"])
     args = [str(arg) for arg in [server_path, *server_args]]
     print(f"bench: starting server with: {' '.join(args)}")
     pkwargs = {