ClippableElement: 7 is a better number than 10

MediaWiki theme popups are bigger than OOUI theme popups, which means
they edge closer to the boundaries of parent elements, which means
that we need to decrease this value. I do not know why this is
implemented with a magic number, but 7 is so much better than 10
anyway.

Bug: T78178
Change-Id: Idc128df3a2db7732bbae5fd63337a44c0bd1a12c
FieldLayout: In styles, don't assume that label is given

Caused ugly spaces in VE's interface where we abuse FieldLayouts.
https://phabricator.wikimedia.org/F21023

Change-Id: Iede750cba53b94615b54ed633ea5eca23cb3a633
TextInputWidget: Set vertical-align: middle, like buttons

Various UIs we have often override their TextInputWidget to be
inline-block (OOUI's styles define them as block elements) and place
them inline with buttons, which already have vertical-align: middle.

This is a problem with the MediaWiki theme, where the height of
buttons and inputs is not the same.

Bug: T78041
Bug: T78052
Change-Id: I7ac1be5c30b3365cf601dbf22da5f4d59c8a57bf
Merge "TextInputWidget: Set vertical-align: middle, like buttons"
Merge "ClippableElement: 7 is a better number than 10"
Merge "FieldLayout: In styles, don't assume that label is given"