feat: implement provider updating

add `v1/providers/` which uses PUT to allow users to change their provider configuration

this is a follow up to #1429 and related to #1359

a user can call something like:

`llama_stack_client.providers.update(api="inference", provider_id="ollama", provider_type="remote::ollama", config={'url': 'http:/localhost:12345'})`

or

`llama-stack-client providers update inference ollama remote::ollama "{'url': 'http://localhost:12345'}"`

this API works by adding a `RequestMiddleware` to the server which checks requests, and if the user is using PUT /v1/providers, the routes are re-registered with the re-initialized provider configurations/methods

for the client, `self.impls` is updated to hold the proper methods+configurations

this depends on a client PR, the CI will fail until then but succeeded locally

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/apis/providers/providers.py

@@ -47,3 +47,8 @@ class Providers(Protocol):
         :returns: A ProviderInfo object containing the provider's details.
         """
         ...
+
+    @webmethod(route="/providers/{api}/{provider_id}/{provider_type}", method="PUT")
+    async def update_provider(
+        self, api: str, provider_id: str, provider_type: str, config: dict[str, Any]
+    ) -> ProviderInfo: ...