v0.2.0: port rack QueryParser

Changes:

• Port https://github.com/rack/rack/blob/main/lib/rack/query_parser.rb to make better compatible with rails/rack
• Port https://github.com/rack/rack/blob/main/test/spec_utils.rb
• Merge JSON with other structured data
• Rename axum_params::ParamsValue -> axum_params::Value, doesn't need use it directly.