Improve #format_lines_for_cloudformation for readability and performance

Co-authored-by: Stanisław Pitucha <stan.pitucha@envato.com>

Author: orien

lib/stack_master/cloudformation_interpolating_eruby.rb

@@ -50,10 +50,7 @@ def format_lines_for_cloudformation(source)
         lines = lines.to_s if lines.is_a?(Symbol)
         next(lines) unless lines.is_a?(String)
 
-        newlines = Array.new(lines.count("\n"), "\n")
-        newlines = lines.split("\n").map { |line| "#{line}#{newlines.pop}" }
-        newlines.insert(0, "\n") if lines.start_with?("\n")
-        newlines
+        lines.scan(/[^\n]*\n?/).reject { |x| x == '' }
       end
     end
   end