Fix type mismatch when ORT_ENABLE_STREAM is off (#14324)
### Description
<!-- Describe your changes. -->
PartitionIntoStreams was incorrectly using std::string instead of
PathString for the config file argument when ORT_ENABLE_STREAM was not
defined.
Also Incorporate changes from #14291 to fix build and test issues.
### 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. -->
Fix build error on Windows due to mismatched type.
