Changes

tmf: Unit-test TmfTraceType.selectExperimentType

Add possible test coverage for the recently added selectExperimentType
in TmfTraceType. Briefly comment where coverage isn't done.

Augment the existing use of TmfExperimentStub for this added purpose.
Base this added validateWithTraces method on the recently introduced
TmfExperiment one. Introduce TmfExperimentSyslog as a supplemental yet
sibling for this same unit testing purpose, just to cover some more.

Fix a minor IDE warning (javadoc) and SonarLint issue (return) locally
in TmfTraceType while there. Fix such minor warnings also in the hereby
touched TraceAndExperimentTypeTest.

Change-Id: Ib7d792ee692e785f3b60158758ff1fc38ce7efcd
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass/org.eclipse.tracecompass/+/203282
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>