perf test record.sh: Raise limit of open file descriptors

perf test record.sh: Raise limit of open file descriptors

Subtest for system-wide record with '--threads=cpu' option fails due
to a limit of open file descriptors on systems with 128 or more CPUs
as the default limit is set to 1024.

The number of open file descriptors should be slightly above
nmb_events*nmb_cpus + nmb_cpus(for perf.data.n) + 4*nmb_cpus(for pipes),
which equals 8*nmb_cpus. Therefore, temporarily raise the limit to
16*nmb_cpus for the test.

Committer notes:

Instead of disabling ShellCheck warnings all the uses of 'uname -n',
i.e. those:

  In tests/shell/record.sh line 35:
  default_fd_limit=$(ulimit -Sn)
                            ^-^ SC3045 (warning): In POSIX sh, ulimit -S is undefined.

We can just switch from using '/bin/sh' to '/bin/bash' for this test, as
bash _has_ 'ulimit -n', so ShellCheck will not emit that warning.

There are dozens of 'perf test' shell tests that do just that,
'/bin/bash' is a reasonable expectation for those tests.

Signed-off-by: Veronika Molnarova <vmolnaro@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Radostin Stoyanov <rstoyano@redhat.com>
Link: https://lore.kernel.org/linux-perf-users/20240429085721.10122-1-vmolnaro@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>