tmf: change ITmfTraceProperties to a more generic ITmfPropertiesProvider

tmf: change ITmfTraceProperties to a more generic ITmfPropertiesProvider

This allow other elements than traces to implement this interface and also
provide properties to display in the UI.

Change-Id: I11fe5bdc4825e2cc548f1d683b21a90e5fd2f3ae
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/65323
Reviewed-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>