Due to an issue when lowering from scf to spirv as there was no conversion pass for index to spirv, we are motivated to add a conversion pass from the Index dialect to the SPIR-V dialect. Furthermore, we add the new conversion patterns to the scf-to-spirv conversion. Fixes https://github.com/llvm/llvm-project/issues/63713 --------- Co-authored-by: Jeremy Kun <jkun@google.com>