[SPIR-V] vk::static_pointer_cast and vk::reinterpret_pointer_cast fail to compile

Description
Currently these two casting functions for buffer pointers don't seem to cast at all - they behave as if their return type is the same as the input type:

<source>:17:29: error: cannot initialize a variable of type 'BufferPointer<Base>' with an rvalue of type 'BufferPointer<Derived>'
    vk::BufferPointer<Base> derivedBufAsBase = vk::static_pointer_cast<Base>(derivedBuf);
                            ^                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:19:30: error: cannot initialize a variable of type 'BufferPointer<float>' with an rvalue of type 'BufferPointer<int>'
    vk::BufferPointer<float> intBufAsFloat = vk::reinterpret_pointer_cast<float>(intBuf);
                             ^               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Steps to Reproduce
https://godbolt.org/z/vTos39Wcx

Environment

• DXC version: trunk
• Host Operating System: Windows 11