onnxruntime

Update pattern matching for EmbedLayerNormalization fusion (#14344)

### Description
This PR addresses the case where an optional Gather node is in the
subgraph pattern. The optional node is now fused with the other nodes
matched in the pattern to create an EmbedLayerNormalization node.



### Motivation and Context
The original subgraph pattern is
```
                      Gather    Gather
                           \   /
                            Add
                             |           
                     LayerNormalization
                             |           
                          Attention
                             |  
                            ...
```
and the new subgraph pattern is
```
                      Gather    Gather
                           \   /
   Gather (optional)        Add
                   \         |           
                     LayerNormalization
                             |           
                          Attention
                             |  
                            ...
```