New timer field for resource monitor and multitest parts merge

[Pyifan]

Bug / Requirement Description

This change is to consolidate timer and event_recorder and get ready for resource monitor. It is also useful for multitest parts merge.

Solution description

1. change timer field from Dict[str, Interval] to Dict[str, List[Interval]]
2. make timer available to (almost) all entities via a recursive link to parent's report
3. remove EventRecorder
4. re-org Report class hierarchy
5. re-org ReportSchema class hierarchy

yet to do:

• ui change
• add test
• new frag
• check info leak

Checklist:

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