CI: more eval/__FILE__ fixes for 3.3.0-preview2

- replace __FILE__ for `envfile.rb` `instance_eval` calls
- add `TODO` for __FILE__ swapping comments

test/multiverse/lib/multiverse/envfile.rb

@@ -18,6 +18,11 @@ def initialize(file_path, options = {})
       @ignore_ruby_version = options[:ignore_ruby_version] if options.key?(:ignore_ruby_version)
       if File.exist?(file_path)
         @text = File.read(self.file_path)
+        # TODO: Test this behavior against Ruby 3.3.0 when it is out of preview
+        #       to see if this behavior persists. Remove the gsub if not.
+        # With Ruby 3.3.0-preview2, eval() yields '(eval ...' as the String value
+        # when __FILE__ is used so swap out __FILE__ for the known agent root path
+        @text.gsub!('__FILE__', "'#{file_path}'")
         instance_eval(@text)
       end
       @gemfiles = [''] if @gemfiles.empty?

test/new_relic/gemspec_files_test.rb

@@ -11,6 +11,8 @@ def test_the_test_agent_helper_is_shipped_in_the_gem_files
 
     gem_spec_file_path = File.expand_path('../../../newrelic_rpm.gemspec', __FILE__)
     gem_spec_content = Gem.open_file(gem_spec_file_path, 'r:UTF-8:-', &:read)
+    # TODO: Test this behavior against Ruby 3.3.0 when it is out of preview
+    #       to see if this behavior persists. Remove the gsub if not.
     # With Ruby 3.3.0-preview2, eval() yields '(eval ...' as the String value
     # when __FILE__ is used so swap out __FILE__ for the known agent root path
     gem_spec_content.gsub!('__FILE__', "'#{gem_spec_file_path}'")