Revert "Special:Preferences: Use OOjs UI" and follow-ups

Revert "Special:Preferences: Use OOjs UI" and follow-ups

The number of issues with the new interface is unacceptable and we
will not be able to fix them reasonably quickly. See subtasks of
T180538 for the list of issues, raised both by the Wikimedia community
and by WMF employees.

I should have pushed back harder against the merging of this half-baked
change with the promise that we'll fix it later. I convinced myself
that the regressions were not so noticeable and that the issues that
were pointed out will in fact be fixed by someone. Predictably,
however, regressions were bad and the only person fixing the issues
was me.

I am not going to work nights to make this page decent again within a
reasonable timeframe; I'm not sure if I'd even be able to since many
issues are problems with the design rather than the implementation. No
one else seems to be working on improving it, therefore I am reverting
the change.

On the bright side, this work has resulted in a number of improvements
to HTMLForm and Preferences code, which are not being reverted here:
<https://gerrit.wikimedia.org/r/#/q/topic:T117781>.

If anyone reattempts this, I recommend gating the new interface behind
a configuration variable and URL parameter, like we did with
$wgOOUIEditPage in the past, and testing thoroughly in production
before enabling it for everyone.

* Revert "Special:Preferences: Use OOjs UI"
  This reverts commit 486e566cfef612de6773df435a74d5fc37e27174.
* Revert "Preferences: Show preview of edit fonts in edit font selector"
  This reverts commit 6634ff729dc7f6d0f541639dbdf3c4d9f786ddf6.
* Revert "Follow-Up Iae63b6994: Add missing editfont dependency"
  This reverts commit ce42fdf151c39f91cf4077673219fa6228a54d7f.
* Revert "Preferences: Improve visual appearance by “unboxing” sections"
  This reverts commit c9415bb0059f4dae4abc5e39a8af844328333120.
* Revert "Remove box-shadow from preference panels for ooui-apex"
  This reverts commit a934b82ca27971e8f0553a7ab7c8ee30fccf3283.
* Revert "Preferences: Don't show the watchlist token; just link to ResetTokens"
  This reverts commit e8c9102fc7b66460c33f643b0dea7190cb89ac83.
* Revert "mw.special.preferences: Make the "Basic information" section more compact"
  This reverts commit d48b7260f30c1ec57046a1f8e4c82057aed45e5f.
* Revert "mw.special.preferences: Widen the dropdown of the "Time zone" field"
  This reverts commit afd5f1417efdd463d86186257c4ec77dd4a442ce.

Bug: T117781
Bug: T180538
Change-Id: I44b5daea1828f71881b5bd35218f5ecb7ab7f36e