perf scripts python: Extact necessary information from process event

The script takes in a sample event dictionary(param_dict) and retrieves
relevant data such as time stamp, PID, TID, and comm for each event.
Also start time is defined as a global variable as it need to be passed
to trace_end for gecko meta information field creation.

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/19910fefcfe4be03cd5c2aa3fec11d3f86c0381b.1689961706.git.anupnewsmail@gmail.com


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