Install released puppet and facter gems

Allow `PUPPET_GEM_VERSION` to be passed as an environment variable,
including the source:

   $ export PUPPET_GEM_VERSION="source:https://rubygems-puppetcore.puppet.com#~> 8.0"
   $ export BUNDLE_RUBYGEMS___PUPPETCORE__PUPPET__COM=forge-key:XXX
   $ bundle install
   $ bundle exec puppet --version
   8.13.1

Author: joshcooper

.github/workflows/unit_tests.yaml

@@ -14,3 +14,4 @@ jobs:
 
   Released:
     uses: "puppetlabs/phoenix-github-actions/.github/workflows/unit_tests_with_released_puppet_gem.yaml@main"
+    secrets: inherit

Gemfile

@@ -3,11 +3,14 @@ source ENV['GEM_SOURCE'] || 'https://rubygems.org'
 def location_for(place_or_version, fake_version = nil)
   git_url_regex = %r{\A(?<url>(https?|git)[:@][^#]*)(#(?<branch>.*))?}
   file_url_regex = %r{\Afile:\/\/(?<path>.*)}
+  source_url_regex = %r{\Asource:(?<url>[^#]*)(#(?<version>.*))?}
 
   if place_or_version && (git_url = place_or_version.match(git_url_regex))
     [fake_version, { git: git_url[:url], branch: git_url[:branch], require: false }].compact
   elsif place_or_version && (file_url = place_or_version.match(file_url_regex))
     ['>= 0', { path: File.expand_path(file_url[:path]), require: false }]
+  elsif place_or_version && (source = place_or_version.match(source_url_regex))
+    [source[:version], { require: false, source: source[:url] }]
   else
     [place_or_version, { require: false }]
   end