perf lock: Look up callchain for the contended locks

The lock contention tracepoints don't provide lock names.  All we can
do is to get stack traces and show the caller instead.  To minimize
the overhead it's limited to up to 8 stack traces and display the
first non-lock function symbol name as a caller.

  $ perf lock report -F acquired,contended,avg_wait,wait_total

                  Name   acquired  contended     avg wait    total wait

   update_blocked_a...         40         40      3.61 us     144.45 us
   kernfs_fop_open+...          5          5      3.64 us      18.18 us
    _nohz_idle_balance          3          3      2.65 us       7.95 us
   tick_do_update_j...          1          1      6.04 us       6.04 us
    ep_scan_ready_list          1          1      3.93 us       3.93 us
  ...

Acked-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>