Apply mw-body-content styles to SurfaceWidget

Changes:
* Override ve.ui.SurfaceWidget for use in MW
* Add mw-body-content class to surface view container
* Assert 1em sizing for surface view container to prevent
  mw-body-content from applying its own sizing
* Add new scripts and styles to RL config

Bug: 71652
Change-Id: Iac86facdc0c7a0e48c0f3617e2f6c2e7f001525e