Fix the header layouts for EntryDetails and Page components
Summary:
This ensures that the header is the correct width, and further that
the text does not disappear when there is no space for the text (so
that it elides as intended).
BUG:413433
BUG:413440
Test Plan:
Without patch: Resize a dialog to make the text not fit, and it disappears
With patch: Resize dialog, text is elided as one would expect, and the header row takes up the correct amount of space
Reviewers: ngraham, KNewStuff, Frameworks, Plasma
Reviewed By: ngraham
Subscribers: ahiemstra, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D25067