Update JS dependencies (#15033)

* Update JS dependencies

- Update all JS dependencies
- For octicons, rename trashcan to trash
- For svgo, migrate to v2 api, output seems to have slightly changed but icons look the same
- For stylelint, update config, fix custom property duplicates
- For monaco, drop legacy Edge support
- For eslint, enable new rules, fix new issues
- For less-loader, remove deprecated import syntax

* update svgo usage in generate-images and rebuild logo.svg with it

web_src/js/features/eventsource.sharedworker.js

@@ -46,9 +46,8 @@ class Source {
   listen(eventType) {
     if (this.listening[eventType]) return;
     this.listening[eventType] = true;
-    const self = this;
     this.eventSource.addEventListener(eventType, (event) => {
-      self.notifyClients({
+      this.notifyClients({
         type: eventType,
         data: event.data
       });