chore(logging)!: use comma as a delimiter (llamastack#3095)

Using commas is much more shell-friendly. A semi-colon is a statement
delimiter and must be escaped.

This change is backwards incompatible but I imagine not many people are
using this. I could be wrong. Looking for feedback.

Author: ashwinb

llama_stack/log.py

@@ -99,7 +99,8 @@ def parse_environment_config(env_config: str) -> dict[str, int]:
         Dict[str, int]: A dictionary mapping categories to their log levels.
     """
     category_levels = {}
-    for pair in env_config.split(";"):
+    delimiter = ","
+    for pair in env_config.split(delimiter):
         if not pair.strip():
             continue