Migrated the following tests from JUnit 4 (CloseTestWindowsRule) to JUnit 5 (CloseTestWindowsExtension):
- Bug264804Test.java
- Bug231304Test.java
- ShowViewMenuTest.java
- Bug410426Test.java
- MenuVisibilityTest.java

Replaced @Rule CloseTestWindowsRule with @ExtendWith(CloseTestWindowsExtension.class) and updated JUnit annotations.