Use Jest for unit tests

[pBouillon]

Issue Summary

Migrate from Karma to Jest as a test engine

Category

- [ ] Bug report
- [ ] Regression
- [ ] Feature suggestion
- [ ] Documentation issue
- [x] Other

Expected Behavior

Remove all references to Karma and use Jest instead

Actual Behavior

Karma is still the default test engine as it was on Angular v15

Steps to Reproduce

• Go to the package.json or the angular.json files
• Observe the references to Karma

Environment

• Browser/Device: N/A
• Node version: N/A
• Version: N/A

Additional Information

Wait for @ngx-flagr/core@16.x for it as Angular 16 introduced Jest as a future replacement

Tim Deschryver has a greate article on it