gnu: Change inputs of core packages to plain lists.
This is transparent: the resulting derivations are unchanged.
* gnu/packages/base.scm (grep, sed, tar, patch, diffutils, glibc/hurd-headers)
(coreutils, gnu-make, make-glibc-utf8-locales): Change input fields to
plain package lists and use 'modify-inputs'.
* gnu/packages/guile.scm (guile-1.8, guile-json-1, guile-json-3)
(guile-gdbm-ffi, guile-sqlite3, guile-bytestructures)
(guile-git, guile-zlib, guile-lzlib, guile-zstd, guile-next): Likewise.
* gnu/packages/mes.scm (nyacc-0.86, nyacc-0.99)
(nyacc, nyacc-1.00.2, mes-0.19, mes, m2-planet): Likewise.