Feature: Change markdown engine to markdown it

This commit removes the old evilstreak markdownjs engine.

- Adds specs to WhiteLister and changes it to stop using globals
    (Fixes large memory leak)
- Fixes edge cases around bbcode handling
- Removes mdtest which is no longer valid (to be replaced with
    CommonMark)
- Updates MiniRacer to correct minor unmanaged memory leak
- Fixes plugin specs

lib/pretty_text.rb

@@ -80,11 +80,7 @@ module PrettyText
     ctx_load(ctx, "#{Rails.root}/app/assets/javascripts/discourse-loader.js")
     ctx_load(ctx, "vendor/assets/javascripts/lodash.js")
     ctx_load_manifest(ctx, "pretty-text-bundle.js")
-
-    if SiteSetting.enable_experimental_markdown_it
-      ctx_load_manifest(ctx, "markdown-it-bundle.js")
-    end
-
+    ctx_load_manifest(ctx, "markdown-it-bundle.js")
     root_path = "#{Rails.root}/app/assets/javascripts/"
 
     apply_es6_file(ctx, root_path, "discourse/lib/utilities")
@@ -152,13 +148,6 @@ module PrettyText
         paths[:S3BaseUrl] = Discourse.store.absolute_base_url
       end
 
-      if SiteSetting.enable_experimental_markdown_it
-        # defer load markdown it
-        unless context.eval("window.markdownit")
-          ctx_load_manifest(context, "markdown-it-bundle.js")
-        end
-      end
-
       custom_emoji = {}
       Emoji.custom.map { |e| custom_emoji[e.name] = e.url }
 
@@ -186,12 +175,14 @@ module PrettyText
 
       buffer << "__textOptions = __buildOptions(__optInput);\n"
 
-      # Be careful disabling sanitization. We allow for custom emails
-      if opts[:sanitize] == false
-        buffer << ('__textOptions.sanitize = false;')
-      end
 
       buffer << ("__pt = new __PrettyText(__textOptions);")
+
+      # Be careful disabling sanitization. We allow for custom emails
+      if opts[:sanitize] == false
+        buffer << ('__pt.disableSanitizer();')
+      end
+
       opts = context.eval(buffer)
 
       DiscourseEvent.trigger(:markdown_context, context)