feat: allow for multiple external provider specs (#3341)

# What does this PR do?

when using the providers.d method of installation users could hand craft
their AdapterSpec's to use overlapping code meaning one repo could
contain an inline and remote impl. Currently installing a provider via
module does not allow for that as each repo is only allowed to have one
`get_provider_spec` method with one Spec returned

add an optional way for `get_provider_spec` to return a list of
`ProviderSpec` where each can be either an inline or remote impl.

Note: the `adapter_type` in `get_provider_spec` MUST match the
`provider_type` in the build/run yaml for this to work.

resolves #3226

## Test Plan

once this merges we need to re-enable the external provider test and
account for this functionality. Work needs to be done in the external
provider repos to support this functionality.

Signed-off-by: Charlie Doern <[email protected]>

Author: cdoern

llama_stack/core/distribution.py

@@ -243,6 +243,7 @@ def get_external_providers_from_module(
                     spec = module.get_provider_spec()
                 else:
                     # pass in a partially filled out provider spec to satisfy the registry -- knowing we will be overwriting it later upon build and run
+                    # in the case we are building we CANNOT import this module of course because it has not been installed.
                     spec = ProviderSpec(
                         api=Api(provider_api),
                         provider_type=provider.provider_type,
@@ -251,9 +252,20 @@ def get_external_providers_from_module(
                         config_class="",
                     )
                 provider_type = provider.provider_type
-                # in the case we are building we CANNOT import this module of course because it has not been installed.
-                # return a partially filled out spec that the build script will populate.
-                registry[Api(provider_api)][provider_type] = spec
+                if isinstance(spec, list):
+                    # optionally allow people to pass inline and remote provider specs as a returned list.
+                    # with the old method, users could pass in directories of specs using overlapping code
+                    # we want to ensure we preserve that flexibility in this method.
+                    logger.info(
+                        f"Detected a list of external provider specs from {provider.module} adding all to the registry"
+                    )
+                    for provider_spec in spec:
+                        if provider_spec.provider_type != provider.provider_type:
+                            continue
+                        logger.info(f"Adding {provider.provider_type} to registry")
+                        registry[Api(provider_api)][provider.provider_type] = provider_spec
+                else:
+                    registry[Api(provider_api)][provider_type] = spec
             except ModuleNotFoundError as exc:
                 raise ValueError(
                     "get_provider_spec not found. If specifying an external provider via `module` in the Provider spec, the Provider must have the `provider.get_provider_spec` module available"