`rb_hash_bulk_insert()` is not exposed in `ruby.h`

[byroot]

Ref: ruby/json#678

I can see it's in the internal hash.h, but it's not exposed in ruby.h.

cc @eregon

[eregon]

It's declared in

truffleruby/lib/cext/include/ruby/internal/intern/hash.h

Line 259 in 11986d0

void rb_hash_bulk_insert(long argc, const VALUE *argv, VALUE hash);

which should be included by ruby.h.
But we don't implement that function yet.