grep tests: move binary pattern tests into their own file

grep tests: move binary pattern tests into their own file

Move the tests for "-f <file>" where "<file>" contains a NUL byte
pattern into their own file. I added most of these tests in
966be95549 ("grep: add tests to fix blind spots with \0 patterns",
2017-05-20).

Whether a regex engine supports matching binary content is very
different from whether it matches binary patterns. Since
2f8952250a ("regex: add regexec_buf() that can work on a non
NUL-terminated string", 2016-09-21) we've required REG_STARTEND of our
regex engines so we can match binary content, but only the PCRE v2
engine can sensibly match binary patterns.

Since 9eceddeec6 ("Use kwset in grep", 2011-08-21) we've been punting
patterns containing NUL-byte and considering them fixed, except in
cases where "--ignore-case" is provided and they're non-ASCII, see
5c1ebcca4d ("grep/icase: avoid kwsset on literal non-ascii strings",
2016-06-25). Subsequent commits will change this behavior.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>