Page: Fix title delegate elision glitch
Implicitly sized items like QtQuick/Text don't play nicely with Loader, and generally with kinda-recursive bindings on Layout.* properties.
This combination of two fixes does the trick:
- Use extra TextMetrics for reliable width/height values.
- Round up text's advance width, so that container loader or layout won't ever round it down (which it did with implicitWidth before).
and also can't reproduce now, but I'm pretty sure I got the same glitch in Discover too.
After: No unnecessary eliding occurs, only when there's not enough space.