Capture test log output and store as attachment

#### I'm submitting a ...
- [ ] bug report
- [x] feature request
- [ ] support request => Please do not submit support request here, see note at the top of this template.

**Feature:**
Capture test log output and store as attachment for every test suite/test case/test step.

The issue names no files, tests, or entry points to inspect. Start by locating the test-result and attachment handling components, then determine how suite, case, and step logs are represented; done means each level's test log is captured and stored as an attachment.

Written by the indexing model from the issue text.