Specify qualifier order in `.clang-format`

Since I saw @miscco suggesting to contributors his preferred ordering of `static` and `constexpr`, I thought we could just automate this using clang-format, which has a corresponding style option [QualifierOrder](https://clang.llvm.org/docs/ClangFormatStyleOptions.html#qualifierorder). This option is not set in our `.clang-format` and also not inherited from the LLVM style.

_Originally posted by @bernhardmgruber in https://github.com/NVIDIA/cccl/pull/1233#discussion_r1603786283_