feat(qb): support ambivalent relationship direction

libs/shared/lib/querybuilder/model/BackendQueryFormat.tsx

libs/shared/lib/querybuilder/model/graphology/model.ts

libs/shared/lib/querybuilder/panel/querybuilder.tsx

...red/lib/querybuilder/pills/customFlowLines/connection.tsx

...r/pills/customFlowPills/relationpill/relation-handles.tsx

...lls/customFlowPills/relationpill/relationpill.module.scss

...ustomFlowPills/relationpill/relationpill.module.scss.d.ts

...lls/customFlowPills/relationpill/relationpill.stories.tsx

...ilder/pills/customFlowPills/relationpill/relationpill.tsx

...shared/lib/querybuilder/query-utils/query2backend.spec.ts

libs/shared/lib/querybuilder/query-utils/query2backend.ts