[mlir][SPIRV] Add Image Operands for Image Instructions

This patch is to add Image Operands in SPIR-V Dialect and also let ImageDrefGather to use Image Operands.

Image Operands are used in many image instructions. "Image Operands encodes what oprands follow, as per Image Operands". And ususally, they are optional to image instructions.

The format of image operands looks like:

    %0 = spv.ImageXXXX %1, ... %3 : f32 ["Bias|Lod"](%4, %5 : f32, f32) -> ...

This patch doesn’t implement all operands (see Section 3.14 in SPIR-V Spec) but provides a skeleton of it. There is TODO in verifyImageOperands function.

Co-authored: Alan Liu <alanliu.yf@gmail.com>

Reviewed by: antiagainst

Differential Revision: https://reviews.llvm.org/D108501