proposal: encoding/json/v2: support typed struct tags #81013

The initial prototype of "encoding/json/v2" supported a format tag option, which resolved many issues. It was removed from the final release in #79071 in favor of using typed struct tags for the feature (#74472).

Since typed struct tags is still in a flux, a formal proposal cannot be yet provided for how it might look in "json/v2", but (for now) this issue exists to collect related issues under this as a parent. Subscribe to the issue for an eventual formal proposal once the timing is right.