perf tools: Move event synthesizing routines to separate .c file

For better grouping, in time we may end up making most of these static,
i.e. generalizing the 'perf record' synthesizing code so that based on
the target it can do the right thing and call the needed synthesizers.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-s9zxxhk40s95pjng9panet16@git.kernel.org


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