tmf: Support trace-specific markers in AbstractTimeGraphView

tmf: Support trace-specific markers in AbstractTimeGraphView

Adds an IMarkerEventSource adapter interface.

Computes the list of adapters when a trace is loaded in the view.

Uses the adapters to get the trace-specific marker events for the
current window range when zooming.

Renames getMarkerList() to getViewMarkerList() to better differentiate
with getTraceMarkerList().

Change-Id: I97e00d5cf8eb0c39b78b04077322e26f7d2a85da
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/58864
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>