Remove HttpStatusCode=OK from WriteAsJsonAsync

[RohitRanjanMS]

Eliminated the default value for HttpStatusCode and removed the overloaded methods for setting HttpStatusCode in the response.

Default Behavior - 200 OK

var responseData = req.CreateResponse();
await responseData.WriteAsJsonAsync(new { message = "Done" });
return responseData;

Return a non-200 response

var responseData = req.CreateResponse(HttpStatusCode.BadRequest);
await responseData.WriteAsJsonAsync(new { message = "An error occurred" });
return responseData;

resolves #776

This is a breaking change, targeting feature/2.x branch.

Pull request checklist

• [x] My changes do not require documentation changes
  • [ ] Otherwise: Documentation issue linked to PR
• [x] My changes should not be added to the release notes for the next release
  • [ ] Otherwise: I've added my notes to release_notes.md
• [x] My changes do not need to be backported to a previous version
  • [ ] Otherwise: Backport tracked by issue/PR #issue_or_pr
• [x] I have added all required tests (Unit tests, E2E tests)