Redo the way that the summary item expand/collapse animation works so
that the items all resize in unison so that when moving from one to
another, the summary area as a whole stays a constant width rather
than wobbling slightly.
(Also rename all references to the "minimum" summary item title width,
since it's not a minimum, it's just the width.)
https://bugzilla.gnome.org/show_bug.cgi?id=630546
0215a449ad