Layout transform: Fix-up QDQ units and add constant folding (microsof…

…t#20685)

### Description

#### Problem 1: Broken Transpose QDQ unit
Layout transform's specialized cost function aggressively pushes down
transposes with channel-first or channel-last perms. This can lead to a
situation where a channel-fist/last Transpose gets stuck after being
pushed through an Unsqueeze node that makes the Transpose's perm no
longer channel-first/last. At this point, the specialized cost function
defers to the default const function, which does not see a need to
continue pushing this transpose node. This breaks the QDQ node units for
both the Unsqueeze and the Transpose: DQ -> Unsqueeze -> Transpose -> Q.

<img width="266" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/19691973/82f8432d-ca27-451b-8c36-c8d87b806e30">


The transpose optimizer should insert a Q -> DQ pair between the
Unsqueeze and Transpose nodes to fix both QDQ node units: DQ ->
Unsqueeze -> Q[new] -> DQ[new] -> Transpose -> Q

<img width="198" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/19691973/5a584bdf-e5db-4622-b3bb-83c060e09261">


#### Problem 2: Inserted Squeeze/Transpose nodes should be constant
folded when possible.
The transpose optimizer inserts Squeeze (and Transpose) ops between an
initializer and a DQ to counteract the effect of Unsqueezing that
initializer if it is consumed by multiple nodes. This results in a graph
where the inserted nodes are not in valid node units:

Original graph where two Mul nodes share a common initializer input:
<img width="456" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/19691973/4b9155ae-e32f-41fc-9136-f953b73e92e7">

Resulting graph after transpose optimization without constant folding:
<img width="452" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/19691973/3c1bfef1-d45f-4d6e-aa19-1c2929eae3f5">

Here, the circled Transpose and Squeeze nodes operate on a quantized
integer type but are not in valid QDQ node units. The solution is to run
constant folding, which results in:
<img width="405" alt="image"
src="https://github.com/microsoft/onnxruntime/assets/19691973/aebdb91f-f38f-4583-adec-33e46126365f">


### Motivation and Context
Improve the layout transformation to allow more models to run on EPs
that prefer the channel-last layout.

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Co-authored-by: Scott McKay <[email protected]>