[feat] Refactor VectorDB class hierarchy for flexibility

embedchain/vectordb/base_vector_db.py

@@ -0,0 +1,10 @@
+class BaseVectorDB:
+    def __init__(self):
+        self.client = self._get_or_create_db()
+        self.collection = self._get_or_create_collection()
+
+    def _get_or_create_db(self):
+        raise NotImplementedError
+
+    def _get_or_create_collection(self):
+        raise NotImplementedError