Issue #2828528 by Wim Leers, droplet, ZeiP, vaplas, tacituseu, samuel.mortenson, michielnugter: Add Quick Edit Functional JS test coverage

Issue #2421427 by samuel.mortenson, droplet, dawehner, nod_, Cottser, Wim Leers, xjm, Gábor Hojtsy, Bojhan, tstoeckler, webchick, naveenvalecha, alexpott, LewisNyman, chris_h, Manjit.Singh, phenaproxima, avitslv, yoroy, tim.plunkett, Mixologic, ipwa, slashrsm: Improve the UX of Quick Editing single-valued image fields