Remove JsonValue.fs from client and migrate to System.Text.Json#576

Copilot wants to merge 4 commits into

devfsprojects/FSharp.Data.GraphQL:devfrom

copilot/remove-jsonvalue-fs-use-system-text-jsonfsprojects/FSharp.Data.GraphQL:copilot/remove-jsonvalue-fs-use-system-text-jsonCopy head branch name to clipboard