onnxruntime

Fix GRU tests (#22716)

### Description
Many GRU tests were being skipped due to an error in
MLOperatorAuthorImpl.cpp. The issue was caused by activation function
names not being capitalized (e.g., ‘sigmoid’), while The AttrValue was
using mixed cases (e.g., ‘Sigmoid’, ‘LeakyRelu’), which resulted in an
‘unsupported activation function’ error in
DMLOperatorRecurrentNeuralNetwork.cpp.
This PR fixes the issue by making the DML EP activation function name
case-insensitive, and capitalizing the activation function names in the
tests.

ref PR: https://github.com/microsoft/onnxruntime/pull/15914
ref bug: https://dev.azure.com/microsoft/OS/_workitems/edit/44571772

### 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. -->

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Co-authored-by: nums11 <numsmt2@gmail.com>