Update rack-cors to 2.x branch

What does this MR do and why?

Update rack-cors to 2.x branch. This brings in Ruby 3.1/3.2 upstream build verification.

Changes:

• Use Rack::Utils::HeaderHash when Rack 2.x is detected
• Refactored codebase
• Support declaring custom protocols in origin
• Lowercased header names as defined by Rack spec
• Fix issue with duplicate headers because of header name case

Links:

• https://github.com/cyu/rack-cors/blob/master/CHANGELOG.md
• https://my.diffend.io/gems/rack-cors/1.1.1/2.0.1

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MR acceptance checklist

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Related to #422672 (closed)