fix!: remove chunk_id property from Chunk class (#3954)

# What does this PR do?

chunk_id in the Chunk class executes actual logic to compute a chunk ID.
This sort of logic should not live in the API spec.

Instead, the providers should be in charge of calling generate_chunk_id,
and pass it to `Chunk`.

this removes the incorrect dependency between Provider impl and API impl

Signed-off-by: Charlie Doern <cdoern@redhat.com>

src/llama_stack/providers/utils/memory/vector_store.py

@@ -196,6 +196,7 @@ def make_overlapped_chunks(
         chunks.append(
             Chunk(
                 content=chunk,
+                chunk_id=chunk_id,
                 metadata=chunk_metadata,
                 chunk_metadata=backend_chunk_metadata,
             )