(chore) [CECO-1754] Fix CI

[tbavelier]

What does this PR do?

• Updates Ubuntu 20.04 runners to latest available image

  • This also requires installing rvm that is no longer present by default in the image

• Pin ffi version to 1.16.3 on nix-platforms as otherwise, 1.7.0 is installed that is not compatible due to a broken dependency ffi-1.17.0 requires rubygems version >= 3.3.22 ffi/ffi#1103: example failure https://app.circleci.com/pipelines/github/DataDog/puppet-datadog-agent/971/workflows/6e490e10-37db-44c2-8017-d19019823699/jobs/28742

  Resolving dependencies.......
  ffi-1.17.0-x86_64-linux-musl requires rubygems version >= 3.3.22, which is
  incompatible with the current version, 2.7.11
  
  Exited with code exit status 5

• Pin rspec-its version on OpenSUSE kitchen test to avoid encountering:

  Step 19/27 : RUN gem install serverspec rspec
   ---> Running in affd00e6d53e
  ERROR:  Error installing serverspec:
          The last version of rspec-its (>= 0) to support your Ruby & RubyGems was 1.3.1. Try installing it with `gem install rspec-its -v 1.3.1` and then running the current command again
          rspec-its requires Ruby version > 3.0.0. The current ruby version is 2.5.0.

Motivation

CI fails as 202201-02 is not a valid tag (was deprecated in January https://discuss.circleci.com/t/linux-image-deprecations-and-eol-for-2024/50177). Available tags https://circleci.com/developer/machine/image/ubuntu-2004

• 2024.08.1
• 2024.05.1
• 2024.04.4
• 2024.01.2
• 2024.01.1
• 2023.10.1
• 2023.07.1
• 2023.04.2
• 2023.02.1
• 2022.10.1
• 202111-02
• current
• edge

Example failure: https://app.circleci.com/pipelines/github/DataDog/puppet-datadog-agent/965/workflows/28ecf2ab-351d-4b1e-a43c-5f48d2fda754/jobs/28570

Describe your test plan

CI should be green