Allow using an "inline" version of Chroma using PersistentClient (#567)

The same code is used (inside providers/remote/memory/chroma/chroma.py)
but it is driven by separate configurations and changes which Chroma
client to use. Note that the dependencies are separate
(`chromadb-client` vs `chromadb` -- the latter is a _much_ heavier
package.)

```
pytest -s -v -m chroma memory/test_memory.py --env CHROMA_DB_PATH=/tmp/chroma_test
pytest -s -v -m chroma memory/test_memory.py --env CHROMA_URL=http://localhost:6001
```

llama_stack/providers/remote/memory/weaviate/weaviate.py

@@ -141,13 +141,6 @@ class WeaviateMemoryAdapter(
         )
         self.cache[memory_bank.identifier] = index
 
-    async def list_memory_banks(self) -> List[MemoryBank]:
-        # TODO: right now the Llama Stack is the source of truth for these banks. That is
-        # not ideal. It should be Weaviate which is the source of truth. Unfortunately,
-        # list() happens at Stack startup when the Weaviate client (credentials) is not
-        # yet available. We need to figure out a way to make this work.
-        return [i.bank for i in self.cache.values()]
-
     async def _get_and_cache_bank_index(self, bank_id: str) -> Optional[BankWithIndex]:
         if bank_id in self.cache:
             return self.cache[bank_id]