community[minor]: Add Initial Support for TiDB Vector Store (#15796)

This pull request introduces initial support for the TiDB vector store.
The current version is basic, laying the foundation for the vector store
integration. While this implementation provides the essential features,
we plan to expand and improve the TiDB vector store support with
additional enhancements in future updates.

Upcoming Enhancements:
* Support for Vector Index Creation: To enhance the efficiency and
performance of the vector store.
* Support for max marginal relevance search. 
* Customized Table Structure Support: Recognizing the need for
flexibility, we plan for more tailored and efficient data store
solutions.

Simple use case exmaple

```python
from typing import List, Tuple
from langchain.docstore.document import Document
from langchain_community.vectorstores import TiDBVectorStore
from langchain_openai import OpenAIEmbeddings

db = TiDBVectorStore.from_texts(
    embedding=embeddings,
    texts=['Andrew like eating oranges', 'Alexandra is from England', 'Ketanji Brown Jackson is a judge'],
    table_name="tidb_vector_langchain",
    connection_string=tidb_connection_url,
    distance_strategy="cosine",
)

query = "Can you tell me about Alexandra?"
docs_with_score: List[Tuple[Document, float]] = db.similarity_search_with_score(query)
for doc, score in docs_with_score:
    print("-" * 80)
    print("Score: ", score)
    print(doc.page_content)
    print("-" * 80)
```

libs/community/tests/unit_tests/vectorstores/test_indexing_docs.py

@@ -55,6 +55,7 @@ def test_compatible_vectorstore_documentation() -> None:
         "Chroma",
         "DashVector",
         "DatabricksVectorSearch",
+        "TiDBVectorStore",
         "DeepLake",
         "Dingo",
         "DocumentDBVectorSearch",

libs/community/tests/unit_tests/vectorstores/test_public_api.py

@@ -64,6 +64,7 @@ _EXPECTED = [
     "SupabaseVectorStore",
     "SurrealDBStore",
     "Tair",
+    "TiDBVectorStore",
     "TileDB",
     "Tigris",
     "TimescaleVector",