ev-view: Add cache for border sizes

Border is a CSS property so it's expensive to call compute border so many times.
3 jobs for cache_border in 17 minutes (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #85862
flatpak

00:16:59

manual #85861
allowed to fail manual
gtk-doc
passed #85860
master

00:03:44