bug: close ReaderStream before creating new one

[Arseha]

Bug Report

YDB Python SDK version: 3.2.2

Current behavior: await reader.commit_with_ack may hangs forever if underlying ReaderStream was recreated

Expected behavior: ReaderStream should be closed before recreation. close method of ReaderStream should also empties _partitions_sessions. Currently the method only closes partition_sessions but not empties it. It may result in trying to commit messages using closed partitions_sessions

Related code:

https://github.com/ydb-platform/ydb/blob/47e31d4cfeab1251302eaae74eb9bba78ac7386d/ydb/public/sdk/python3/ydb/_topic_reader/topic_reader_asyncio.py#L162-L172