OZG-7872 move test functions to util file

...rc/e2e/main-tests/postfach-mail/postfach-mail-error.cy.ts

...-e2e/src/e2e/main-tests/postfach-mail/postfach-mail.cy.ts

...c/e2e/main-tests/postfach-mail/postfach-nachrichten.cy.ts

...ofile/user-profile-icon-in-postfach-nachricht-error.cy.ts

.../e2e/main-tests/vorgang-list/vorgang-list-ungelesen.cy.ts

...src/e2e/main-tests/vorgang-list/vorgang-list.search.cy.ts

...ient/apps/alfa-e2e/src/support/postfach-nachricht.util.ts

...t/apps/alfa-e2e/src/support/vorgang-attached-item-util.ts