issue: #36858
- Start channel manager on datacoord, but with empty assign policy in
streaming service.
- Make collection at dropping state can be recovered by flusher to make
sure that
milvus consume the dropCollection message.
- Add backoff for flusher lifetime.
- remove the proxy watcher from timetick at rootcoord in streaming
service.
Also see the better fixup: #37176
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Signed-off-by: chyezh <chyezh@outlook.com>