feat: add deps dynamically based on metastore config (#2405)

# What does this PR do?


## Test Plan
changed metastore in one of the templates, rerun distro gen, observe
change in build.yaml

llama_stack/templates/postgres-demo/build.yaml

@@ -21,4 +21,5 @@ distribution_spec:
 image_type: conda
 additional_pip_packages:
 - asyncpg
+- psycopg2-binary
 - sqlalchemy[asyncio]

llama_stack/templates/template.py

@@ -186,8 +186,14 @@ class DistributionTemplate(BaseModel):
         additional_pip_packages: list[str] = []
         for run_config in self.run_configs.values():
             run_config_ = run_config.run_config(self.name, self.providers, self.container_image)
+
+            # TODO: This is a hack to get the dependencies for internal APIs into build
+            # We should have a better way to do this by formalizing the concept of "internal" APIs
+            # and providers, with a way to specify dependencies for them.
             if run_config_.inference_store:
                 additional_pip_packages.extend(run_config_.inference_store.pip_packages)
+            if run_config_.metadata_store:
+                additional_pip_packages.extend(run_config_.metadata_store.pip_packages)
 
         if self.additional_pip_packages:
             additional_pip_packages.extend(self.additional_pip_packages)