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/resolver.py

@@ -5,9 +5,9 @@
 # the root directory of this source tree.
 import importlib
 import inspect
-import logging
 from typing import Any, Dict, List, Set
 
+from llama_stack import logcat
 from llama_stack.apis.agents import Agents
 from llama_stack.apis.benchmarks import Benchmarks
 from llama_stack.apis.datasetio import DatasetIO
@@ -50,8 +50,6 @@ from llama_stack.providers.datatypes import (
     VectorDBsProtocolPrivate,
 )
 
-log = logging.getLogger(__name__)
-
 
 class InvalidProviderError(Exception):
     pass
@@ -128,7 +126,7 @@ async def resolve_impls(
         specs = {}
         for provider in providers:
             if not provider.provider_id or provider.provider_id == "__disabled__":
-                log.warning(f"Provider `{provider.provider_type}` for API `{api}` is disabled")
+                logcat.warning("core", f"Provider `{provider.provider_type}` for API `{api}` is disabled")
                 continue
 
             if provider.provider_type not in provider_registry[api]:
@@ -136,11 +134,12 @@ async def resolve_impls(
 
             p = provider_registry[api][provider.provider_type]
             if p.deprecation_error:
-                log.error(p.deprecation_error, "red", attrs=["bold"])
+                logcat.error("core", p.deprecation_error)
                 raise InvalidProviderError(p.deprecation_error)
 
             elif p.deprecation_warning:
-                log.warning(
+                logcat.warning(
+                    "core",
                     f"Provider `{provider.provider_type}` for API `{api}` is deprecated and will be removed in a future release: {p.deprecation_warning}",
                 )
             p.deps__ = [a.value for a in p.api_dependencies] + [a.value for a in p.optional_api_dependencies]
@@ -214,10 +213,10 @@ async def resolve_impls(
         )
     )
 
-    log.info(f"Resolved {len(sorted_providers)} providers")
+    logcat.debug("core", f"Resolved {len(sorted_providers)} providers")
     for api_str, provider in sorted_providers:
-        log.info(f" {api_str} => {provider.provider_id}")
-    log.info("")
+        logcat.debug("core", f" {api_str} => {provider.provider_id}")
+    logcat.debug("core", "")
 
     impls = {}
     inner_impls_by_provider_id = {f"inner-{x.value}": {} for x in router_apis}
@@ -354,7 +353,7 @@ def check_protocol_compliance(obj: Any, protocol: Any) -> None:
                 obj_params = set(obj_sig.parameters)
                 obj_params.discard("self")
                 if not (proto_params <= obj_params):
-                    log.error(f"Method {name} incompatible proto: {proto_params} vs. obj: {obj_params}")
+                    logcat.error("core", f"Method {name} incompatible proto: {proto_params} vs. obj: {obj_params}")
                     missing_methods.append((name, "signature_mismatch"))
                 else:
                     # Check if the method is actually implemented in the class