DEV: Update linting setup and fix issues (#17345)

Re-lands #16119 and #17298

* Update eslint-config-discourse
* Update linting workflow
* Prettier-ignore stuff
* Update template-lint config
* Auto-fix template issues
* Fix various template issues
  Mostly incorrect attributes and unused templates
* Prettier js files
* Fix template auto-fix regressions
* Small css tweak

Co-authored-by: Peter Wagenet <peter.wagenet@gmail.com>

.github/workflows/linting.yml

@@ -86,8 +86,9 @@ jobs:
         if: ${{ always() }}
         run: |
           yarn ember-template-lint \
-            app/assets/javascripts \
-            plugins/**/assets/javascripts
+            --no-error-on-unmatched-pattern \
+            "app/assets/javascripts/**/*.hbs" \
+            "plugins/**/assets/javascripts/**/*.hbs"
 
       - name: English locale lint (core)
         if: ${{ always() }}