Remove OpenStruct usage with Struct replacement

[javierjulio]

This replacement to use a struct should still resolve the original issue in #49 but also with #49 (comment) for the reported ruby core issue.

Example you can try in an IRB console:

data = {
  a: 1,
  b: 2,
  c: {
    d: 3,
    e: {
      f: 4,
      g: 5
    }
  }
}

class Hash
  def to_struct
    Struct.new(*self.keys).new(*self.values.map { |value| value.is_a?(Hash) ? value.to_struct : value })
  end
end

result = data.to_struct

[javierjulio]

Since #49 also introduced the json gem dependency, I believe that can be removed here since OpenStruct is no longer used. If desired, I can remove the gemspec dependency here.

[ilyazub]

I'm wondering if to_struct is even needed. It converts the notification passed to the group_started method. It looks like, RSpec::Core::Notifications::GroupNotification can be used instead.

@smileart Do you remember why RSpec::Core::Notifications::GroupNotification was not used instead in #7?

[ilyazub]

json gem is used TurboTests::JsonRowsFormatter#JsonRowsFormatter to provide to_json method, similarly to the RSpec::Core::Formatters::JsonFormatter#close method.

[deivid-rodriguez]

Oh, indeed! Sounds like we still need json then!

[deivid-rodriguez]

Nice! I don't know the root cause of the ruby-core issue, but this direction feels like a nice regardless.

[ilyazub]

Thank you, @javierjulio!

I'll merge this PR and address to_struct removal later (ref: https://github.com/serpapi/turbo_tests/pull/53/files#r1567009884),

[javierjulio]

@ilyazub you're welcome and thank you! That sounds good if it's not needed then.