Upgrade to FontAwesome 5 (take two) (#6673)

* Add missing icons to set

* Revert FA5 revert

 This reverts commit 42572ff

* use new SVG syntax in locales

* Noscript page changes (remove login button, center "powered by" footer text)

* Cast wider net for SVG icons in settings

- include any _icon setting for SVG registry (offers better support for plugin settings)

- let themes store multiple pipe-delimited icons in a setting

- also replaces broken onebox image icon with SVG reference in cooked post processor

* interpolate icons in locales

* Fix composer whisper icon alignment

* Add support for stacked icons

* SECURITY: enforce hostname to match discourse hostname

This ensures that the hostname rails uses for various helpers always matches
the Discourse hostname

* load SVG sprite with pre-initializers

* FIX: enable caching on SVG sprites

* PERF: use JSONP for SVG sprites so they are served from CDN

This avoids needing to deal with CORS for loading of the SVG

Note, added the svg- prefix to the filename so we can quickly tell in
dev tools what the file is

* Add missing SVG sprite JSONP script to CSP

* Upgrade to FA 5.5.0

* Add support for all FA4.7 icons

- adds complete frontend and backend for renamed FA4.7 icons

- improves performance of SvgSprite.bundle and SvgSprite.all_icons

* Fix group avatar flair preview

- adds an endpoint at /svg-sprites/search/:keyword

- adds frontend ajax call that pulls icon in avatar flair preview even when it is not in subset

* Remove FA 4.7 font files

test/javascripts/lib/icon-library-test.js.es6

@@ -0,0 +1,34 @@
+import {
+  iconHTML,
+  iconNode,
+  convertIconClass
+} from "discourse-common/lib/icon-library";
+
+QUnit.module("lib:icon-library");
+
+QUnit.test("return icon markup", assert => {
+  assert.ok(iconHTML("bars").indexOf('use xlink:href="#bars"') > -1);
+
+  const nodeIcon = iconNode("bars");
+  assert.equal(nodeIcon.tagName, "svg");
+  assert.equal(
+    nodeIcon.properties.attributes.class,
+    "fa d-icon d-icon-bars svg-icon svg-node"
+  );
+});
+
+QUnit.test("convert icon names", assert => {
+  const fa47Icon = convertIconClass("fa-clock-o");
+  assert.ok(iconHTML(fa47Icon).indexOf("far-clock") > -1, "FA 4.7 syntax");
+
+  assert.ok(
+    iconHTML("area-chart").indexOf("chart-area") > -1,
+    "renamed FA 4.7 icons"
+  );
+
+  const fa5Icon = convertIconClass("fab fa-facebook");
+  assert.ok(iconHTML(fa5Icon).indexOf("fab-facebook") > -1, "FA 5 syntax");
+
+  const iconC = convertIconClass("  fab fa-facebook  ");
+  assert.ok(iconHTML(iconC).indexOf("  ") === -1, "trims whitespace");
+});