ExtractorTransformer: more info-level logging

[ForNeVeR]

Pull Request Details

Description

This adds info-level logging for every meaningful stage of ExtractorTransformer, improving the observability of what happens in there. Also, seeing exact hashes is useful at times.

Related Issue

Closes #1660.

Motivation and Context

How Has This Been Tested

If it compiles (and passes the tests) then it works. Right?

(Well, in this case at least I believe so.)

Types of changes

• [ ] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have included my change in the CHANGELOG.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[hsz]

Thanks!