Resource oriented design for shields (#399)

* init

* working bedrock tests

* bedrock test for inference fixes

* use env vars for bedrock guardrail vars

* add register in meta reference

* use correct shield impl in meta ref

* dont add together fixture

* right naming

* minor updates

* improved registration flow

* address feedback

---------

Co-authored-by: Dinesh Yeduguru <dineshyv@fb.com>

llama_stack/providers/inline/agents/meta_reference/safety.py

@@ -37,7 +37,7 @@ class ShieldRunnerMixin:
         responses = await asyncio.gather(
             *[
                 self.safety_api.run_shield(
-                    identifier=identifier,
+                    shield_id=identifier,
                     messages=messages,
                 )
                 for identifier in identifiers