OPERA PCM Release Candidate 3.0 for R1

What's Changed

• Explain PCM meaning by @riverma in #163
• DSWx-HLS PGE 1.0.0-rc.2.0 update by @collinss-jpl in #165
• Set payload_hash in isl lambda function with S3 eTag value to avoid duplicate ingest staged job submission

Full Changelog: 1.0.0-rc.2.0...1.0.0-rc.3.0