feat(provider): add multiple option support in ProviderConfig

- Introduced a new field `multiple` in the `ProviderConfig` class to allow for multiple selections, enhancing the configuration capabilities for providers.
- This addition improves flexibility in provider settings and aligns with the evolving requirements for provider configurations.

api/core/entities/provider_entities.py

@@ -194,6 +194,7 @@ class ProviderConfig(BasicProviderConfig):
     required: bool = False
     default: Optional[Union[int, str, float, bool, list]] = None
     options: Optional[list[Option]] = None
+    multiple: bool | None = False
     label: Optional[I18nObject] = None
     help: Optional[I18nObject] = None
     url: Optional[str] = None