perf test: Introduce workloads__for_each()

perf test: Introduce workloads__for_each()

And use it in run_workload().

Testing it:

  root@x1:~# perf trace -e *landlock* perf test -w landlock
       0.000 ( 0.015 ms): :1274331/1274331 landlock_add_rule(ruleset_fd: 11, rule_type: LANDLOCK_RULE_PATH_BENEATH, rule_attr: 0x7ffd3fea55e0, flags: 45) = -1 EINVAL (Invalid argument)
       0.018 ( 0.003 ms): :1274331/1274331 landlock_add_rule(ruleset_fd: 11, rule_type: LANDLOCK_RULE_NET_PORT, rule_attr: 0x7ffd3fea55f0, flags: 45) = -1 EINVAL (Invalid argument)
  root@x1:~# perf test -w bla
  No workload found: bla
  root@x1:~#

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Clark Williams <williams@redhat.com>
Link: https://lore.kernel.org/r/20241020021842.1752770-2-acme@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>