BS-8277
Fix dandling references after migration from v5

Conflicts:
	bundles/plugins/org.bonitasoft.studio.importer.bar/src/org/bonitasoft/studio/importer/bar/custom/migration/WidgetMigration.java
	bundles/plugins/org.bonitasoft.studio.importer.bar/src/org/bonitasoft/studio/importer/bar/processor/EdaptBarToProcProcessor.java
	bundles/plugins/org.bonitasoft.studio.migration/src/org/bonitasoft/studio/migration/utils/StringToExpressionConverter.java