Pass through 'helpInline' to OOUI FieldLayout and make true by default

Pass through 'helpInline' to OOUI FieldLayout and make true by default

This change is meant to improve the layout of Special:Preferences in
particular, but it will affect any OOUI form using help messages. It
should be a harmless or beneficial change for most of them.

Previous behavior can be restored by passing `'help-inline' => false`
to the HTMLForm factory after 'help-message'/'help-messages'/'help'.

For example:

* Special:Preferences?ooui=1#mw-prefsection-watchlist
  * Before: https://phabricator.wikimedia.org/F25025213
  * After:  https://phabricator.wikimedia.org/F25025181

* Special:ChangeEmail
  * Before: https://phabricator.wikimedia.org/F25073327
  * After:  https://phabricator.wikimedia.org/F25073328

* Special:BotPasswords/foo
  * Before: https://phabricator.wikimedia.org/F25073324
  * After:  https://phabricator.wikimedia.org/F25073326

Bug: T181854
Change-Id: Ica67fe4081dfaa8eb9e8f56fdb93530750e47012