tmf: Merge TmfDataProvider and TmfEventProvider together

tmf: Merge TmfDataProvider and TmfEventProvider together

Initially, there was a plan to support "traces" that had no timestamps,
and this would be handled by a DataProvider. Turns out the whole
framework requires some sort of timestamp nowadays, so this distinction
is no longer necessary.

(If a trace really does not have any timestamp, they could just use the
event rank as a sort of dummy timestamp, which is quite intuitive anyway).

This also merges Tmf{Data|Event}Request and TmfCoalesced{Data|Event}Request.

Change-Id: I734bb297d252d56902e1eb0534669b0d4088d911
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/17052
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
IP-Clean: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>