refactor ntp to use brave-ui

[cezaraugusto]

Changes in this pull-request:

• Replace all legacy LESS files for NTP
• Make NTP responsive
• Simplify logic for background images
• Remove leftover files

Test Plan 1 - change default new tab and private new tab structure

• New tab (default) should render;
• Private tab (default) should render;
• Private tab (default) shoud toggle between default search engine/ddg;
• Tor window should render.

Test Plan 2 - refactor new tab page to use brave-ui

close brave/brave-browser#633

• All interactions in new tab top sites should work

  • Tile links to its website;
  • Pinning/unpinning;
  • Bookmarking/un-bookmarking;
  • Removing
    • All actions in the removal notification should work

• Background should change upon browser refresh

• Background should load even without internet connection

• Links in footer should go to their own links

Test Plan 3 - remove leftover files from ntp

• Ensure everything builds -- should be catched by CI

Test Plan 4 - adapt favicon size to 64px to match tile icon size

This is a tentative to make favicons look better without much success, but since favicon image wrapper has 64px I thought to be a good idea to have the same size fetched by Brave

[petemill]

@cezaraugusto nice refactoring - is this ready for review?

[petemill]

@cezaraugusto ...or does it depend on brave/brave-ui#344?

[cezaraugusto]

hey @petemill yes ready now. re brave/brave-ui#344 it has some breaking changes that would be better landing once this PR is reviewed. here I'm using the sha from that PR so not required to have it merged to check out this branch

[cezaraugusto]

after a push force github auto closed this pr and can't let me re-open. I'll create a new one

[cezaraugusto]

new PR #1339