onnxruntime

[CoreML EP] Minor changes to allow CoreML EP to handle more nodes and models. (#15993)

### Description
<!-- Describe your changes. -->

Minor changes to allow CoreML EP to handle more nodes and models.
- Remove graph input dynamic shape check from
coreml::GetSupportedNodes(). Each node input is still checked.
- Add check for optional input in coreml::IsInputSupported(). If an
input does not exist it should not be considered unsupported.

### 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. -->

Some CoreML EP checks seem too strict now.