issue: #42098#42404
related to: ##42009 #41937
Implement new method to handle partition removal from next target
without directly modifying current target.
Changes include:
- Add RemovePartitionFromNextTarget method and deprecate RemovePartition
- Update target_observer to use new method for ReleasePartition
operations
- Add unit tests and mock methods for new functionality
This ensures that all changes to next target will propagates to
delegator's query view.
Signed-off-by: Wei Liu <wei.liu@zilliz.com>