Show up to three file item actions inline, not just one

Right now when there is more than one file item action, all of them get dumped into a sub-menu. Because both Konsole and Gwenview install plugins, and most Plasma installations include these apps, most users experience the file item action plugins in sub-menu form.

Using a sub-menu when there is more than one item feels a bit excessive. Showing up to three inline should avoid bloating the menu too much while still handling the rare cases when there are tons and tons of items

BUG: 424281 FIXED-IN: 5.73

File item plugins now shown inline when there are two: