chore: Add fixtures to conftest.py (#2067)

Add fixtures for SqliteKVStore, DiskDistributionRegistry and
CachedDiskDistributionRegistry. And use them in tests that had all been
duplicating similar setups.

## Test Plan
unit tests continue to run

Signed-off-by: Derek Higgins <derekh@redhat.com>

tests/unit/fixtures.py

@@ -0,0 +1,34 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import pytest
+
+from llama_stack.distribution.store.registry import CachedDiskDistributionRegistry, DiskDistributionRegistry
+from llama_stack.providers.utils.kvstore.config import SqliteKVStoreConfig
+from llama_stack.providers.utils.kvstore.sqlite import SqliteKVStoreImpl
+
+
+@pytest.fixture(scope="function")
+async def sqlite_kvstore(tmp_path):
+    db_path = tmp_path / "test_kv.db"
+    kvstore_config = SqliteKVStoreConfig(db_path=db_path.as_posix())
+    kvstore = SqliteKVStoreImpl(kvstore_config)
+    await kvstore.initialize()
+    yield kvstore
+
+
+@pytest.fixture(scope="function")
+async def disk_dist_registry(sqlite_kvstore):
+    registry = DiskDistributionRegistry(sqlite_kvstore)
+    await registry.initialize()
+    yield registry
+
+
+@pytest.fixture(scope="function")
+async def cached_disk_dist_registry(sqlite_kvstore):
+    registry = CachedDiskDistributionRegistry(sqlite_kvstore)
+    await registry.initialize()
+    yield registry