Put genbki.pl output into src/include/catalog/ directly

Put genbki.pl output into src/include/catalog/ directly

With the makefile rules, the output of genbki.pl was written to
src/backend/catalog/, and then the header files were linked to
src/include/catalog/.

This changes it so that the output files are written directly to
src/include/catalog/.  This makes the logic simpler, and it also makes
the behavior consistent with the meson build system.  Also, the list
of catalog files is now kept in parallel in
src/include/catalog/{meson.build,Makefile}, while before the makefiles
had it in src/backend/catalog/Makefile.

Reviewed-by: Andreas Karlsson 
Discussion: https://www.postgresql.org/message-id/flat/21b74bdc-183d-4dd5-9c27-9378d178f459@eisentraut.org