tmf: Make time graph combo item heights dynamically linked

tmf: Make time graph combo item heights dynamically linked

The height of items in the time graph control are dynamically linked to
the height of their corresponding tree items. This ensures alignment
when tree items have different heights due to custom fonts or images.

Change-Id: I84a2394f6d5673bec1af9a2858cc0a31a76f2753
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/15107
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
IP-Clean: Bernd Hufmann <bernd.hufmann@ericsson.com>