t0210: refactor trace2 scrubbing to not use Perl

t0210: refactor trace2 scrubbing to not use Perl

The output generated by our trace2 mechanism contains several fields
that are dependent on the environment they're being run in, which makes
it somewhat harder to test it. As a countermeasure we scrub the output
and strip out any fields that contain such information.

The logic to do so is implemented in Perl, but it can be trivially
ported to instead use sed(1). Refactor the code accordingly so that we
can drop the PERL_TEST_HELPERS prerequisite.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>