Interpreter support for quantized type

[sdasgup3]

fixes #2373

The PR is rebased on top on #2383 and cherry-pick changes from #2384.

Direction to reviewer

Please review the commit 4d7dc1a excluding the following files

• docs/generated/stablehlo_passes.md
• stablehlo/transforms/Passes.td
• stablehlo/transforms/ShapeLegalizeToStablehlo.cpp

[mlevesquedion]

I think this approach is fine, but I thought the point of the reference interpreter was to show how the various operations work. Would it be much more onerous to implement support for uniform_quantize and uniform_dequantize directly?

[sdasgup3]

I think this approach is fine, but I thought the point of the reference interpreter was to show how the various operations work. Would it be much more onerous to implement support for uniform_quantize and uniform_dequantize directly?

That is a very good point!
Even if we support uniform_{de}quantize operations we still need support for other quantized operations, like add with quantized type, in the interpreter.

The idea here is to handle all the quantized operation uniformly. That means, either

(A) Support the execution semantics of all the quantized operations (uniform_quantize, uniform_dequantize, and any other operations which support quantized types) natively in the interpreter, OR
(B) Apply the pass uniformly to lower any quantized operations.

(B) is the fastest path towards evaluating quantize program.