Instrument Nokogiri parsing methods

What does this MR do?

This MR instruments the various parsing methods of Nokogiri.

Are there points in the code the reviewer needs to double check?

No.

Why was this MR needed?

This allows us to see how much time is spent in Nokogiri.

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together