[WebGPU EP] allow concat operator to handle large number of inputs (#25390)
### Description
<!-- Describe your changes. -->
Adjusts concat operator to batch inputs based on
maxStorageBuffersPerShaderStage to allow unlimited number of inputs.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Fixes patchtst model for transformers.js
<img width="960" height="367"
alt="{31C75CD1-7A7D-48E3-A090-FB153925D165}"
src="https://github.com/user-attachments/assets/f5772709-80b7-4a05-8927-40f496be908c"
/>