kdig: add EDNS0 Padding and query alignment support

doc/man/kdig.1in

doc/man_kdig.rst

src/libknot/rrtype/opt.h

src/utils/common/exec.c

src/utils/common/exec.h

src/utils/kdig/kdig_exec.c

src/utils/kdig/kdig_params.c

src/utils/kdig/kdig_params.h

tests/libknot/test_edns.c