feat: migrate firefox to resource API

[damacus]

Summary

• migrate cookbook usage from top-level recipes/attributes to the firefox_install custom resource API
• add migration, limitations, and resource documentation
• modernize CI/Kitchen platforms and use the Sous Chefs shared Cinc Workstation installer

Verification

• berks install
• cookstyle
• chef exec rspec --format documentation
• yamllint .
• markdownlint-cli2 '**/*.md'
• KITCHEN_LOCAL_YAML=kitchen.dokken.yml kitchen list
• KITCHEN_LOCAL_YAML=kitchen.dokken.yml kitchen test --destroy=always, with post-fix reruns for affected suites

[github-actions]

Slowest examples

Top 10 slowest examples (0.52 seconds, 83.28% of total time)

Example	Description	Time in seconds
spec/default_spec.rb:67	firefox_install with default settings on RHEL is expected to install package "firefox"	0.1616
spec/default_spec.rb:15	firefox_install with default settings on Ubuntu is expected to add apt_repository "mozilla"	0.0536
spec/default_spec.rb:30	firefox_install with version specified on Ubuntu is expected to install package "firefox"	0.0464
spec/default_spec.rb:56	firefox_install with Mozilla repository management disabled on Debian is expected not to add apt_repository "mozilla"	0.04115
spec/default_spec.rb:77	firefox_install with default settings on openSUSE is expected not to add zypper_repository "mozilla"	0.03965
spec/default_spec.rb:78	firefox_install with default settings on openSUSE is expected to install package "firefox"	0.03858
spec/default_spec.rb:16	firefox_install with default settings on Ubuntu is expected to create file "/etc/apt/preferences.d/mozilla"	0.03581
spec/default_spec.rb:43	firefox_install with upgrade action specified on Ubuntu is expected to upgrade package "firefox"	0.03484
spec/default_spec.rb:18	firefox_install with default settings on Ubuntu is expected to install package "firefox"	0.03431
spec/default_spec.rb:17	firefox_install with default settings on Ubuntu is expected to nothing apt_update "mozilla"	0.0342