Re-Add firefox to CI

[mrdrogdrog]

Component/Part

CI E2E

Description

This PR re-adds firefox to the CI . We had firefox in before but it caused a lot of trouble like crashing and way longer runs. This PR should test if it got any better in the meantime.

Steps

• Added / updated tests
• I read the contribution documentation and
  made sure that:
  • My commits are signed-off to accept the DCO.
  • This PR targets the correct branch: master for 1.x & docs, develop for 2.x

[codecov]

Codecov Report

Merging #4964 (22c9655) into develop (f786fe5) will not change coverage.
Report is 5 commits behind head on develop.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #4964   +/-   ##
========================================
  Coverage    57.44%   57.44%           
========================================
  Files          405      405           
  Lines        11691    11691           
  Branches       969      969           
========================================
  Hits          6716     6716           
  Misses        4921     4921           
  Partials        54       54           

Flag	Coverage Δ
backend	89.32% <ø> (ø)
backend-e2e-tests	75.38% <ø> (ø)
backend-unit-tests	85.72% <ø> (ø)
e2e-tests	75.38% <ø> (ø)
frontend	38.76% <ø> (ø)
frontend-unit-tests	38.76% <ø> (ø)
unit-tests	51.41% <ø> (ø)

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[ErikMichelson]

The CI failure seems to be a somewhat not deterministic issue (cypress-io/cypress#8611)?