feat: use Nokogiri's HUGE parse option

[flavorjones]

In sparklemotion/nokogiri#2865, which upgrades the latest libxml2 release, I started seeing failures that seem related to the larges sizes of the valgrind output files generated by Nokogiri's test suite:

Nokogiri::XML::SyntaxError: 360080:11: FATAL: internal error: Huge input lookup
/__w/nokogiri/nokogiri/lib/nokogiri/xml/reader.rb:99:in `read'
/__w/nokogiri/nokogiri/lib/nokogiri/xml/reader.rb:99:in `each'
/usr/local/bundle/gems/ruby_memcheck-1.3.1/lib/ruby_memcheck/test_task_reporter.rb:34:in `block in parse_valgrind_output'
/usr/local/bundle/gems/ruby_memcheck-1.3.1/lib/ruby_memcheck/test_task_reporter.rb:33:in `each'
/usr/local/bundle/gems/ruby_memcheck-1.3.1/lib/ruby_memcheck/test_task_reporter.rb:33:in `parse_valgrind_output'

I haven't dug in too much as to why libxml2 2.11.0 is complaining about this, but a lot of the buffering code got rewritten. See the release notes for more information, but the work is being described as:

Refactoring has begun on some buffering and encoding code with the goal of simplifying this part of the code base and improving error reporting.

In any case, setting the HUGE parse option will avoid these errors, at the cost of a slight performance tradeoff.