[Repo Assist] Add JSON SaveOptions property tests + STJ benchmark prototype (#1671)#1694

dsyme merged 2 commits intomainfsprojects/FSharp.Data:mainfrom

repo-assist/improve-json-tests-and-stj-bench-20260313-f29e1e3425191501fsprojects/FSharp.Data:repo-assist/improve-json-tests-and-stj-bench-20260313-f29e1e3425191501Copy head branch name to clipboard