tmf: Introduce the notion of PID to the Callstack analysis

tmf: Introduce the notion of PID to the Callstack analysis

The current Callstack View/Analysis does not handle PIDs (process IDs)
only TIDs (thread IDs).

This works fine with the basic use case of a trace with only one,
single-threaded process. But since callstacks are per thread, but
symbol resolution is per-process, the callstack analysis should be
augmented to know about both concepts.

Change-Id: I6a6ad5f92e18c3c161390237b8dea513dc9ce8cf
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/69870
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>