prevent undefined behaviour of SPIR-V Backend non-asserts builds when dealing...

prevent undefined behaviour of SPIR-V Backend non-asserts builds when dealing with token type (#78437)

The goal of this PR is to fix the issue when use of token type in LLVM
intrinsic causes undefined behavior of SPIR-V Backend code generator
when assertions are disabled:
https://github.com/llvm/llvm-project/issues/78434

Among possible fix options, discussed in the
https://github.com/llvm/llvm-project/issues/78434 issue description, the
option to generate a meaningful error before execution arrives at the
`llvm_unreachable` call looks like a better solution for now, because
SPIR-V doesn't support token type anyway without additional extensions.

The PR is to generate a user-friendly error message and exit without
generating a stack dump when such a usage of token type was detected
that would lead to undefined behavior of SPIR-V Backend code generator.