[Mobile Benchmark Test] Add os, job_arn, and job_conclusion to artifact (#6371)

#6294

Details:
- print `os` in test spect printout section
- store os, job_arn (mobile job) and job_conclusion to each artifact
metadata. Notice this is not github job conclusion, this is mobile job
conclusion.
- wrap post-test logics into ReportProcessor, 
    - pass aws client as parameter for test-driven purpose
    - add unit test for ReportProcessor

Author: yangw-dev