feat: add a configurable category-based logger (#1352)

A self-respecting server needs good observability which starts with
configurable logging. Llama Stack had little until now. This PR adds a
`logcat` facility towards that. Callsites look like:

```python
logcat.debug("inference", f"params to ollama: {params}")
```

- the first parameter is a category. there is a static list of
categories in `llama_stack/logcat.py`
- each category can be associated with a log-level which can be
configured via the `LLAMA_STACK_LOGGING` env var.
- a value `LLAMA_STACK_LOGGING=inference=debug;server=info"` does the
obvious thing. there is a special key called `all` which is an alias for
all categories

## Test Plan

Ran with `LLAMA_STACK_LOGGING="all=debug" llama stack run fireworks` and
saw the following:


![image](https://github.com/user-attachments/assets/d24b95ab-3941-426c-9ea0-a4c62542e6f0)

Hit it with a client-sdk test case and saw this:


![image](https://github.com/user-attachments/assets/3fee8c6c-986e-4125-a09c-f5dc019682e2)

llama_stack/distribution/stack.py

@@ -5,7 +5,6 @@
 # the root directory of this source tree.
 
 import importlib.resources
-import logging
 import os
 import re
 from typing import Any, Dict, Optional
@@ -13,6 +12,7 @@ from typing import Any, Dict, Optional
 import yaml
 from termcolor import colored
 
+from llama_stack import logcat
 from llama_stack.apis.agents import Agents
 from llama_stack.apis.batch_inference import BatchInference
 from llama_stack.apis.benchmarks import Benchmarks
@@ -39,8 +39,6 @@ from llama_stack.distribution.resolver import ProviderRegistry, resolve_impls
 from llama_stack.distribution.store.registry import create_dist_registry
 from llama_stack.providers.datatypes import Api
 
-log = logging.getLogger(__name__)
-
 
 class LlamaStack(
     VectorDBs,
@@ -101,12 +99,11 @@ async def register_resources(run_config: StackRunConfig, impls: Dict[Api, Any]):
         objects_to_process = response.data if hasattr(response, "data") else response
 
         for obj in objects_to_process:
-            log.info(
+            logcat.debug(
+                "core",
                 f"{rsrc.capitalize()}: {colored(obj.identifier, 'white', attrs=['bold'])} served by {colored(obj.provider_id, 'white', attrs=['bold'])}",
             )
 
-    log.info("")
-
 
 class EnvVarError(Exception):
     def __init__(self, var_name: str, path: str = ""):