FieldLayout: Use <label> for this.$body, not this.$element

We don't want this.$help inside the <label>, because clicking/hovering
on the help icon triggers click/hover effects on the InputWidget.
(It doesn't actually get clicked, but the UI looks as if it was.)

Change-Id: I701423149f4839a9d96005546dc74bb665294998
Account for <html> rather than <body> being the scrollable root in Chrome

Follow-up to 2674d311.

Bug: T70370
Change-Id: I5396f976db112c015c7b6104fd79c98c38420257
GridLayout: Don't round to 1%

1% of a today's screens is a lot and things look misaligned.

Change-Id: Ic5d3c7c218059a69d8857516f5bdbf5a6339c73d
Merge "GridLayout: Don't round to 1%"