Reland: "[mlir][index][spirv] Add conversion for index to spirv" (#69790)

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



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Co-authored-by: Jeremy Kun <jkun@google.com>