Add single-benchmark execute, simplify compilation

performance/benchmarks/fizzbuzz_10000.rb

@@ -1,10 +1,7 @@
 # frozen_string_literal: true
 
-Benchmarks.define('fizzbuzz_10000', Class.new do
-  TEMPLATE = <<~LIQUID
-  {% for i in (1..10000) %}{{ i }}
-  {% endfor %}
-  LIQUID
+Benchmarks.define('simple_loop', Class.new do
+  TEMPLATE = "{% for i in (1..1000) %}{{ i }}{% endfor %}"
 
   def compile
     @parsed = Liquid::Template.parse(TEMPLATE)