feat: add to_list and to_pandas api's (#556)

Add `to_list` to return query results as list of python dict (so we're
not too pandas-centric). Closes #555

Add `to_pandas` API and add deprecation warning on `to_df`. Closes #545

Co-authored-by: Chang She <chang@lancedb.com>

docs/src/examples/serverless_lancedb_with_s3_and_lambda.md

@@ -80,14 +80,14 @@ def handler(event, context):
     # Shape of SIFT is (128,1M), d=float32
     query_vector = np.array(event['query_vector'], dtype=np.float32)
 
-    rs = table.search(query_vector).limit(2).to_df()
+    rs = table.search(query_vector).limit(2).to_list()
 
     return {
         "statusCode": status_code,
         "headers": {
             "Content-Type": "application/json"
         },
-        "body": rs.to_json()
+        "body": json.dumps(rs)
     }
 ```