Log more usage statistics

Since the string 'Peak memory use' is kept, this should be ok'ish with
respect to backwards compatible search statements in the log

src/ert/__main__.py

@@ -637,7 +637,7 @@ def log_process_usage() -> None:
             "Swaps": usage.ru_nswap,
             "Peak memory use (KB)": maxrss,
         }
-        logger.info(f"Peak memory use: {maxrss} KB", extra=usage_dict)
+        logger.info(f"Ert process usage: {usage_dict}")
     except Exception as exc:
         logger.warning(
             f"Exception while trying to log ERT process resource usage: {exc}"