tmf: Rework TmfTraceUtils#resolveIntEventAspectOfClassForEvent

tmf: Rework TmfTraceUtils#resolveIntEventAspectOfClassForEvent

The generic type bound now ensures the aspect class passsed to
resolveIntEventAspectOfClassForEvent() really resolves to an
Integer, which means we can skip the check.

Also rework both aspect-finding methods to use flat Stream operations.

Change-Id: I8a341021699a69ac21b7a147c9ea91d58619fa99
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/69856
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>