perf shell completion: Restrict completion of events to events

perf shell completion: Restrict completion of events to events

'perf list' will list libpfm4 events and metrics which aren't valid
options to the '-e' option. Restrict the events gathered so that invalid
ones aren't shown.

Before:

  $ perf stat -e <tab><tab>
  Display all 633 possibilities? (y or n)

After:

  $ perf stat -e <tab><tab>
  Display all 375 possibilities? (y or n)

Committer testing:

  # grep -m1 'model name' /proc/cpuinfo
  model name	: AMD Ryzen 9 5950X 16-Core Processor
  #

Before:

  # . tools/perf/perf-completion.sh
  # perf stat -e
  Display all 2672 possibilities? (y or n)

After:

  # . tools/perf/perf-completion.sh
  # perf stat -e
  Display all 2648 possibilities? (y or n)

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20230905181554.3202873-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>