Allow float bias with Conv QDQ node group

[qti-ashimaj]

Description

Allow bias to be float when selecting QDQ node group for Conv Op

Motivation and Context

If the bias is float (non-quantized) while the weights and activations are quantized, the Q and DQ nodes aren't getting properly partitioned into 1 group along with the conv op. As a result, graph finalization error occurs. This change will allow the node group to be formed even when bias is float.

The bias quantization is handled in #483

[qti-chuteng]

🟠 Major

[M-1] onnxruntime/core/providers/qnn/qnn_ep_utils.cc → OrtConvNodeGroupSelector::Check()

The semantic change to allow dq_nodes.size() == 2 (float-bias Conv) is a functional bug fix with a clear regression risk, but the PR diff contains no unit test. Per team convention, a bug-fix PR must include a reproducing test (CI red), a post-fix verification (CI green), and a kill-test fence — temporarily reverting the fix to confirm the test fails. Without a test, a future accidental revert to the default num_dq_inputs = -1 would go undetected.

Please add two test cases in onnxruntime/test/providers/qnn/:

1. Float bias: Conv + DQ(input) + DQ(weight), bias as a float initializer (no DQ node) → assert Check() returns true
2. INT32 bias regression: Conv + DQ(input) + DQ(weight) + DQ(bias, INT32) → confirm existing behavior is unchanged

Record the kill-test result in the PR description's Validation section.

---

🔵 Minor

[N-1] onnxruntime/core/providers/qnn/qnn_ep_utils.cc:L853

After passing static_cast<int>(dq_nodes.size()) as num_dq_inputs, the "reject if DQ count mismatches" guard inside CheckQDQNodes becomes a no-op (the passed value always equals the actual value). If Check() is ever called with dq_nodes.size() < 2, CheckQDQNodes can no longer intercept it, and the subsequent dq_nodes[0] at L858 / dq_nodes[1] at L859 would be out-of-bounds.

  if (!CheckQDQNodes(graph, ort_api, node, redundant_clip_node, dq_nodes, q_nodes, static_cast<int>(dq_nodes.size()))) {
    return false;
  }

  if (dq_nodes.size() < 2) {
    return false;  // Conv requires at least DQ nodes for input and weight
  }