### Add Object Store Integration and Access Layer Factory
- **Cargo.lock, Cargo.toml**: Added `object-store` as a dependency to integrate object storage capabilities.
- **frontend.rs, instance.rs, builder.rs, server.rs**: Introduced `ObjectStoreConfig` and `AccessLayerFactory` to manage object storage configurations and access layers.
- **access_layer.rs**: Made `AccessLayerFactory` clonable and its constructor public to facilitate object store access layer creation.
- **prom_store.rs**: Updated `PromBulkState` to include `AccessLayerFactory` and modified `remote_write` to utilize the access layer for processing requests.
- **lib.rs**: Made `access_layer` module public to expose access layer functionalities.
Signed-off-by: Lei, HUANG <mrsatangel@gmail.com>