perf scripts python: Implement add sample function and thread processing

The stack has been created for storing func and dso from the callchain.
The sample has been added to a specific thread. It first checks if the
thread exists in the Thread class. Then it call _add_sample function
which is responsible for appending a new entry to the samples list.

Also callchain parsing and storing part is implemented. Moreover removed
the comment from thread.

Signed-off-by: Anup Sharma <anupnewsmail@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/5a112be85ccdcdcd611e343f6a7a7482d01f6299.1689961706.git.anupnewsmail@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>