Added Move Nested Member refactoring

[oleg68]

Summary

• added a K2-native Move Nested Member workflow for nested classes/objects and companion functions/properties
• added a structured target chooser, fresh K2 target discovery, atomic multi-file updates, and Undo Last Refactoring support
• allowed nested classes/objects to move into bodyless target classes/objects, creating a target body automatically
• restricted the command to the Refactor menu and covered the bodyless-target regression

Validation

• mvn clean test — passed (863 tests)
• mvn package -DskipTests — passed; produced Nbm/target/nbm/netbeans-plugin-kotlin-nbm-0.11.260-SNAPSHOT.nbm
• git diff --check — passed
• python3 build-scripts/update-copyright.py --check — passed

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