tmf: Introduce IOnDemandAnalysisReport and corresponding element

tmf: Introduce IOnDemandAnalysisReport and corresponding element

For now the ReportsElement will be responsible for tracking which
reports are currently available. This means they are not persisted
and will be lost on restart. A future improvement could be to move
this logic to the trace so they can be saved as supplementary files.

Change-Id: I6c896665c7e4f43155aa499e59dc93d296e3119e
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/71562
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>