Update EmberJS Version

[Robin481]

We are quite a bit behind now and should probably update the EmberJS version.

As this is hard to plan without knowing what changes in all the different versions this should probably be done in a timeboxed manner for a few versions at a time.

For now timeboxed to 24 hours
TODO:

• Update Ember Versions step by step
• Keep Update Node LTS Version #496 in mind as you probably need to update the Node Version along the way anyways.
• Check that in this new state the EmberJS specific security advisories are also fixed
• Upgrade Boostrap to 4 or even 5
• Make sure tests still pass after each step
• Smoke Tests after each step

[lkleisa]

Long time ago (today), someone took 16 hours time to upgrade our emberjs frontend. It went well until version 3.28.0.
This ticket was stopped with the result of a new branch and an upgrade of emberjs from 3.17.0 to 3.24.0. Node stayed the same on this branch (on the new, there is an upgrade from 12 to 14).
There were multiple errors after the upgrade to emberjs 3.28.0, and I tried to fix them step by step.
What I tried after emberjs 3.24.0 (on the new branch):

• Commit 60a4eb7: I've updated ember-cli-string-helpers from 2.0.0 to 6.1.0
• Commit 5deba21: I've updated @ember/test-helpers from 1.7.1 to 2.9.3
• Commit 5deba21: I've updated node version from 12 to 14 (locally, I used v14.19.0)
• Commit d661eb4: I've updated ember-qunit from 4.1.1 to 6.2.0
• Commit 600c8e2: I've upgraded emberjs version from 3.24.0 to 3.28.0
  After this, there was a problem, which is still a bug from ember: [Bug] Some addons fail ember:try scenarios with ember-release (3.25) with loc$$1.sliceStartChars is not a function emberjs/ember.js#19432
  Therefore, I've set the bootstrap version in frontend/ember-cli-build.js to 3, updated ember-bootstrap from 3.1.1 to 4.9.0 and ember-popper from 0.10.3 to 0.11.3
  After this, there was a problem with font awesome. Because last ember-font-awesome support was 4 years ago, it's recommended to use FortAwesome. The problem is, that we use ember-font-awesome in another dependency (ember-cli-icon-rating). Because of that, I forked ember-cli-icon-rating and replaced ember-font-awesome with ember-fontawesome. This fork is here.
  I've added the fork in package.json. I don't know if the change to ember-fontawesome works 100% in puzzle skills, but the fork of its own works.
  Now, there is a problem while ember build, which I couldn't fix in this 16 hours.