Make embedding generation go through inference (#606)

This PR does the following:
1) adds the ability to generate embeddings in all supported inference
providers.
2) Moves all the memory providers to use the inference API and improved
the memory tests to setup the inference stack correctly and use the
embedding models

This is a merge from #589 and #598

llama_stack/providers/tests/memory/conftest.py

@@ -6,9 +6,65 @@
 
 import pytest
 
+from ..conftest import get_provider_fixture_overrides
+
+from ..inference.fixtures import INFERENCE_FIXTURES
 from .fixtures import MEMORY_FIXTURES
 
 
+DEFAULT_PROVIDER_COMBINATIONS = [
+    pytest.param(
+        {
+            "inference": "meta_reference",
+            "memory": "faiss",
+        },
+        id="meta_reference",
+        marks=pytest.mark.meta_reference,
+    ),
+    pytest.param(
+        {
+            "inference": "ollama",
+            "memory": "pgvector",
+        },
+        id="ollama",
+        marks=pytest.mark.ollama,
+    ),
+    pytest.param(
+        {
+            "inference": "together",
+            "memory": "chroma",
+        },
+        id="chroma",
+        marks=pytest.mark.chroma,
+    ),
+    pytest.param(
+        {
+            "inference": "bedrock",
+            "memory": "qdrant",
+        },
+        id="qdrant",
+        marks=pytest.mark.qdrant,
+    ),
+    pytest.param(
+        {
+            "inference": "fireworks",
+            "memory": "weaviate",
+        },
+        id="weaviate",
+        marks=pytest.mark.weaviate,
+    ),
+]
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--inference-model",
+        action="store",
+        default=None,
+        help="Specify the inference model to use for testing",
+    )
+
+
 def pytest_configure(config):
     for fixture_name in MEMORY_FIXTURES:
         config.addinivalue_line(
@@ -18,12 +74,22 @@ def pytest_configure(config):
 
 
 def pytest_generate_tests(metafunc):
+    if "inference_model" in metafunc.fixturenames:
+        model = metafunc.config.getoption("--inference-model")
+        if not model:
+            raise ValueError(
+                "No inference model specified. Please provide a valid inference model."
+            )
+        params = [pytest.param(model, id="")]
+
+        metafunc.parametrize("inference_model", params, indirect=True)
     if "memory_stack" in metafunc.fixturenames:
-        metafunc.parametrize(
-            "memory_stack",
-            [
-                pytest.param(fixture_name, marks=getattr(pytest.mark, fixture_name))
-                for fixture_name in MEMORY_FIXTURES
-            ],
-            indirect=True,
+        available_fixtures = {
+            "inference": INFERENCE_FIXTURES,
+            "memory": MEMORY_FIXTURES,
+        }
+        combinations = (
+            get_provider_fixture_overrides(metafunc.config, available_fixtures)
+            or DEFAULT_PROVIDER_COMBINATIONS
         )
+        metafunc.parametrize("memory_stack", combinations, indirect=True)