3369 fix missing ids no command
- UniqueIdUtils:
- Remove fixMissingIDs(final ITopLevelElement modelElement) (only used in one place)
- fixMissingIDs(EObject object, EObject existingModel): Do not wrap model modification into a command. This is up to the caller of this method (e.g., the command stack is not available in tests)
- Remove IDMigrationProvider: Fixup of missing / duplicated is handled in ModelContext
- ModelContext: Use nonDirtyingCommand, and automatically save model in case IDs have been fixed