oeqa: write @OETestTag content into json test reports for each case

This allows using these tags for classification and filtering of test results
according to various organization-specific criteria, such as teams
responsible for the test, internal test ids, feature domains and so on.

Test name itself meanwhile can stay short and human-readable.

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>