[filesapp] Add files-ng specific SVG icons

  arrow_{up,down}_small.svg file list sort up and down arrows
    16px x 16px filled with Grey 700 #5F6368
  dragger.svg: used for splitter bar, and file list column drag
    32px x 32px filled with Grey 300 #DADCE0
  drag_drop_{allow,deny}.svg drag drop chip allow and deny icon
    20px x 20px filled with white #fff

  Optimized these SVG icon with SVGOMG.

Bug: 1002393, 1002790, 992821
Change-Id: Ie01d8836b7f59f832f9aefcfecba8591b791207e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1916537Reviewed-by: Noel Gordon <noel@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715595}

ui/file_manager/file_manager/foreground/images/common/arrow_down_small.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
+  <path fill="#5F6368" d="M7.2 10.85L3.39 6.84 2.4 7.86 8 13.6l5.6-5.74-.99-1.02-3.81 4.01V2.4H7.2z"/>
+</svg>

ui/file_manager/file_manager/foreground/images/common/arrow_up_small.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16">
+  <path fill="#5F6368" d="M8.8 5.15l3.81 4.01.99-1.02L8 2.4 2.4 8.14l.99 1.02L7.2 5.15v8.45h1.6z"/>
+</svg>

ui/file_manager/file_manager/foreground/images/common/drag_drop_allow.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 20 20">
+  <path fill="#fff" d="M11 4v5h5v2h-5v5H9v-5H4V9h5V4h2z"/>
+</svg>

ui/file_manager/file_manager/foreground/images/common/drag_drop_deny.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 20 20">
+  <path fill="#fff" d="M10 3a7 7 0 110 14 7 7 0 010-14zm-5 7a5 5 0 007.757 4.172l-6.929-6.93A4.977 4.977 0 005 10zm5-5c-1.02 0-1.967.305-2.757.828l6.929 6.93A5 5 0 0010 5z"/>
+</svg>

ui/file_manager/file_manager/foreground/images/common/dragger.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32">
+  <path fill="#DADCE0" d="M13.5 19.5c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S12 21.825 12 21s.675-1.5 1.5-1.5zm5 0c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S17 21.825 17 21s.675-1.5 1.5-1.5zm-5-5c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S12 16.825 12 16s.675-1.5 1.5-1.5zm5 0c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S17 16.825 17 16s.675-1.5 1.5-1.5zm-5-5c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S12 11.825 12 11s.675-1.5 1.5-1.5zm5 0c.825 0 1.5.675 1.5 1.5s-.675 1.5-1.5 1.5S17 11.825 17 11s.675-1.5 1.5-1.5z"/>
+</svg>