Add MacOS build to ORT C Pod (#18550)
### Description
<!-- Describe your changes. -->
As title.
1. Add macos build as an optionally enabled arch for pod and changes to
exsiting build_ios_framework/assemble_c_pod scripts.
2. Enable macos build arch in ios packaging pipeline (currently for
variants other than Mobile) and check the output artifacts are correct.
3. Write MacOS Test Target scheme in the test app and integrate into ios
packaging CI testing pipeline.
Currently the changes only apply to onnxruntime-c pod. as the original
request was from ORT SPM which consumes the onnxruntime-c pod only as
the binary target. TODO: could look into adding macos platform to objc
pod as well.
### 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. -->
Enable macos platform support in cocoapods. and also potentially produce
binary target for enabling macos platform in SPM as well.
Replace https://github.com/microsoft/onnxruntime/pull/18334
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Co-authored-by: rachguo <rachguo@rachguos-Mac-mini.local>
Co-authored-by: rachguo <rachguo@rachguos-Mini.attlocal.net>
Co-authored-by: Edward Chen <18449977+edgchen1@users.noreply.github.com>
