libchrome: JsonReader::ReadAndReturnValueWithError return base::expected

Migration for the function to return base::expected instead of
base::JSONReader::ValueWithError is completed.
Cherry-pick the upstream change r1017954 and remove the forward
compatibility change that added stubs to the old struct.

BUG=b:238297537
TEST=CQ

Change-Id: I1ef95216b1f45a525710fcd34c765d76cff21387
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/libchrome/+/3882043
Commit-Queue: Grace Cham <hscham@chromium.org>
Tested-by: Grace Cham <hscham@chromium.org>
Reviewed-by: Qijiang Yūki Ishii <fqj@google.com>