Replace Gen_dummy_probes.sed with Gen_dummy_probes.pl

Replace Gen_dummy_probes.sed with Gen_dummy_probes.pl

To generate a dummy probes.h file when dtrace is not available, we had
two different scripts: A sed version, which is the original version,
and a Perl version, which was generated by s2p.  This split was
necessary because Perl was not a mandatory build dependency on Unix,
but sed was not guaranteed to be available on Windows.

(The Meson build system used the sed version even on Windows, which
was probably incorrect and probably would have had to be fixed before
elevating that build system from experimental status.)

As of 721856ff24, Perl is a required build dependency, so this split
is no longer necessary.  We can just use the Perl script in all build
environments and remove a whole bunch of infrastructure to keep the
two variants in sync.

The new Gen_dummy_probes.pl is not the version generated by s2p but a
new implementation written by hand by adapting the sed version to Perl
syntax.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/3fd0f1bc-4483-4ba9-8aa0-64765b052039@eisentraut.org