Arith to ModArith Conversion pass and Mac Transformer pass

[WoutLegiest]

• Adding conversion pass to convert arith into mod arith; now limited operations are supported.
  Conversion is place in the Arith folder, but lives in the heir::arith dialect
• Transformation pass in mod-arith to find consecutive mul and add operations and replace them with a Mac operation
• Pipeline pass for Tosa to secret/Arith i32

The arith-to-mod-arith pass is required to lower a neural network TOSA model to a CGGI backend. This pass will transform the operations to the mod-arith dialect, where the find-mac pass can be used to convert consecutive multiply addition operations into a single operation. In a later pass (ongoing work), these large precision MAC operations (typically 64 or 32-bit) will be lowered into small precision (8 or 4b) operations that can be mapped to CGGI operations.

[j2kun]

Looks like some tests are failing. Could you fix that and then send the PR to me for review?

[j2kun]

One thing I think would be helpful is an explanation (perhaps in the PR description, maybe also in the tablegen pass description field) of the broader reason for having this pass. What e2e use case is it intended to support, and what stage of that e2e use case is it managing?

[j2kun]

@WoutLegiest is this ready for a final review?

[WoutLegiest]

@WoutLegiest is this ready for a final review?

Yes it is!

[AlexanderViand-Intel]

I don't think I fully understand why this TOSA pipeline needs to use mod_arith but I already have some ideas for howto (ab)use ArithToModArith so super happy to see it :)