D3D: Remove ResourceSerial The only difference between ResourceSerial and UniqueueSerial (formerly Serial) appears to be ResourceSerial is wrapper of object pointer. This CL removes ResourceSerial class and switched it to UniqueSerial class instead. (We may need to see why it needs to use pointer to initialize the serial, that sounds like the exact thing serial try to avoid.) Bug: b/262047600 Change-Id: Ic8e1b26d7da9304ff02fd9a7e1b584bb70efcb77 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4102107 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Charlie Lao <cclao@google.com>