[onert/python] Add CI job to validate ONERT python API #15344
Description
What
Add a CI job that runs pytest tests/ to automatically validate the ONERT Python inference API (infer.session(), tensorinfo bindings, infer(..., measure=True), etc.) on every pull request.
Why
Currently there is no CI job to validate the Python API. However, this issue is not related to CI, so that’s fine. Running the sample code manually provides sufficient testing for this issue.
Originally posted by @ragmani in #15172
Tests Draft : #15343