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/admin/components/themes-list-item-test.js.es6

@@ -11,7 +11,7 @@ componentTest("default theme", {
 
   test(assert) {
     assert.expect(1);
-    assert.equal(this.$(".fa-check").length, 1, "shows default theme icon");
+    assert.equal(this.$(".d-icon-check").length, 1, "shows default theme icon");
   }
 });
 
@@ -26,11 +26,15 @@ componentTest("pending updates", {
 
   test(assert) {
     assert.expect(1);
-    assert.equal(this.$(".fa-refresh").length, 1, "shows pending update icon");
+    assert.equal(
+      this.$(".d-icon-refresh").length,
+      1,
+      "shows pending update icon"
+    );
   }
 });
 
-componentTest("borken theme", {
+componentTest("broken theme", {
   template: "{{themes-list-item theme=theme}}",
   beforeEach() {
     this.set(
@@ -45,7 +49,7 @@ componentTest("borken theme", {
   test(assert) {
     assert.expect(1);
     assert.equal(
-      this.$(".fa-exclamation-circle").length,
+      this.$(".d-icon-exclamation-circle").length,
       1,
       "shows broken theme icon"
     );