[llvm] [SPIRV] Implement support for SPV_KHR_expect_assume (PR #66217)

[Michal Paszkowski via llvm-commits]

https://github.com/michalpaszkowski approved this pull request.

Thank you @pmatos for the patch and thank you @iliya-diyachkov for the comments! The patch LGTM!

One last thing before you merge, please add the missing lines at the end of `IntrinsicsSPIRV.td` and `assume.ll` files for consistency.

https://github.com/llvm/llvm-project/pull/66217