pdn: add DEF golden check to pads_black_parrot_macro_grid test

Add write_def + diff_files against a committed .defok so the test also
guards the full generated layout, not just the pad-connection count.

Addresses @gadfort review on #10722.

Signed-off-by: Saurav Singh <saurav.singh@fermions.co>

Author: saurav-fermions