Disable rendering of tag based on register (#1162)

* Disable rendering of tag based on register

* Improvements to disable tag

* Resolve disbale tag tests

* Test disable_tags register

* disabled_tags is now always avaiable

* Allow multiple tags to be disabled at once

* Move disabled check to block_body

* Code improvements

* Remove redundant nil check

* Improve disabled tag error output

* Improve disable tag API

* Code improvements

* Switch disabled? to not mutate output

* Fix array handling shortcut in disable_tags

lib/liquid/variable.rb

@@ -104,6 +104,14 @@ module Liquid
       output
     end
 
+    def disabled?(_context)
+      false
+    end
+
+    def disabled_tags
+      []
+    end
+
     private
 
     def parse_filter_expressions(filter_name, unparsed_args)