Feature/logfile assertions

[zhenyu-ms]

Bug / Requirement Description

Clearly and concisely describe the problem.

Solution description

Describe your code changes in detail for reviewers.

Checklist:

• [x] Test
• [x] Example (both test_plan.py and .rst)
• [x] Documentation (API)
• [x] News fragment present for release notes
• [x] MS info leakage check
• [ ] For new driver: driver index page
• [x] For new assertion: ui/pdf/std renderers, documentation
• [ ] For new cmdline arg: documentation