Vulkan: Switch DescriptorPoolPointer to use SharedPtr To make the reference counting easier to maintain, SharedPtr class is added to automatically tracking the reference counting and object creation/destruction. Right now we have BindingPointer class doing similar things except it does not automatically manage the object create/destroy, which makes it less robust as well as redundant code to manage object life cycle. The other problem with BindingPointer is that it does not work with normal assign/copy operator which made it hard to read and use. SharedPtr uses exact same API semantics as std::shared_ptr, which makes the reference counting very easy to use. The main difference of SharedPtr and std::shared_ptr is that it does not use any atomic or lock since it assumes user only uses it under thread safe environment, which ANGLE's backend is. This CL also changes mDescriptorPools to mDynamicDescriptorPools to make it clear that it is dynamic descriptor pool not the descriptor pool. This is also preparation CL for the next CL where we will use SharedPtr to manage DescriptorSetHelper life cycle, which otherwise a bit complicated to manually manage. Bug: angleproject:372268711 Change-Id: I1033d9bf259bbc075a9b374d8a28e1f67d889873 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5926183 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>