lttng: Rename the debug-info callsite aspect to "source callsite"

lttng: Rename the debug-info callsite aspect to "source callsite"

If not all debug information is available in the binary, it is possible
to only display the "binary file/symbol/offset" tuple. The latter will
be named "binary callsite", to differentiate it from the complete
source callsite.

Change-Id: Ie7e0368a6b1c02c63f759536728835f464ea463b
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/58775
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>