feat: add custom embedding types and migrate providers

- introduce baseembeddingsprovider and helper for embedding functions  
- add core embedding types and migrate providers, factory, and storage modules  
- remove unused type aliases and fix pydantic schema error  
- update providers with env var support and related fixes

src/crewai/rag/embeddings/providers/roboflow/__init__.py

@@ -0,0 +1,15 @@
+"""Roboflow embedding providers."""
+
+from crewai.rag.embeddings.providers.roboflow.roboflow_provider import (
+    RoboflowProvider,
+)
+from crewai.rag.embeddings.providers.roboflow.types import (
+    RoboflowProviderConfig,
+    RoboflowProviderSpec,
+)
+
+__all__ = [
+    "RoboflowProvider",
+    "RoboflowProviderConfig",
+    "RoboflowProviderSpec",
+]