[tosa] : Add e2e support for quantized matmul.

[sahas3]

This PR enables e2e test for quantized torch.mm and it's other variants through the tosa path.

torch IR for quantized matmul is shown in the following snippet:

%2 = torch.aten._make_per_tensor_quantized_tensor %0, %float2.150000e-02, %int-25 : !torch.vtensor<[3,4],si8>, !torch.float, !torch.int -> !torch.vtensor<[3,4],!torch.qint8>
  %3 = torch.aten._make_per_tensor_quantized_tensor %1, %float1.760000e-02, %int18 : !torch.vtensor<[4,3],si8>, !torch.float, !torch.int -> !torch.vtensor<[4,3],!torch.qint8>
  %4 = torch.aten.mm %2, %3 : !torch.vtensor<[3,4],!torch.qint8>, !torch.vtensor<[4,3],!torch.qint8> -> !torch.vtensor<[3,3],!torch.qint32>
  %5 = torch.aten.int_repr %4 : !torch.vtensor<[3,3],!torch.qint32> -> !torch.vtensor<[3,3],si32>
  %6 = torch.aten._make_per_tensor_quantized_tensor %5, %float3.784000e-04, %int0 : !torch.vtensor<[3,3],si32>, !torch.float, !torch.int -> !torch.vtensor<[3,3],!torch.qint32>
  %7 = torch.aten.dequantize.tensor %6 : !torch.vtensor<[3,3],!torch.qint32> -> !torch.vtensor<[3,3],f32>

1. This change adds legalizations for _make_per_tensor_quantized_tensor, int_repr which are basically cast operations. The former op carries the zero-point/scale information for (de)quantizing values.
2. Legalization for dequantize.tensor is also added which is the usual dequantization op.
3. Legalization for matmul is fixed to infer the zero-point information from the source _make_per_tensor_quantized_tensor ops for the matmul operands. Scale doesn't need to be considered, as it will be taken care of correctly at the output via FuseQuantizedOps transform.

[sahas3]

Hi @sjarus, a gentle reminder to take a look at this PR when you have a chance. Thanks!

[sjarus]

Sorry for the delay! My github notifications aren't always reliable.

[sahas3]

Sorry for the delay! My github notifications aren't always reliable.

No worries, thanks for the review!