Fix simulation of .prepend() in ve.ce.BranchNode#onSplice

Unrolling jQuery's .prepend() for performance is a good idea, but it
helps to implement it correctly. It was inserting elements in
reverse order, oops!

Change-Id: Ic0de79f591a2c921796a1e7bac50543d1f6733d9
[BREAKING CHANGE] Remove generated content node wrappers

This prevents us from ending up with CE HTML like
<div><tr>...</tr></div>.

Remove all styles directly attached to GC nodes.

Bug: 67169
Change-Id: I60eb5d82e0114c38dfd3ce2b7bbda8aadb1ca2d6
Merge "Fix simulation of .prepend() in ve.ce.BranchNode#onSplice"
Merge "[BREAKING CHANGE] Remove generated content node wrappers"