[llvm] [SPIR-V] Add cl_khr_kernel_clock / SPV_KHR_shader_clock extension (PR #92771)

[Vyacheslav Levytskyy via llvm-commits]

VyacheslavLevytskyy wrote:

@svenvh Thank you and very glad to see this contribution! My only suggestions are about the test case, with a general goal to make it slightly cleaner, devoid of unimportant details -- otherwise PR looks good.

https://github.com/llvm/llvm-project/pull/92771