issue: https://github.com/milvus-io/milvus/issues/38877
1. refactor pymilvus client v2 testcasebase
2. add a test for search hint
3. update pymilvus to 2.6
---------
Signed-off-by: yanliang567 <yanliang.qiao@zilliz.com>
related issue: #36963
1. add alias tests with rename collection for issue #36963
2. update some test levels
3. fix some xfail tests
---------
Signed-off-by: yanliang567 <yanliang.qiao@zilliz.com>