Tweak test data for signed package installation

Tweak test data for signed package installation

* test/lisp/emacs-lisp/package-resources/signed/signed-bad-1.0.el:
* test/lisp/emacs-lisp/package-resources/signed/signed-good-1.0.el:
Use lexical-binding.
* test/lisp/emacs-lisp/package-resources/signed/update-signatures.sh:
New file.
* test/lisp/emacs-lisp/package-resources/key.pub:
* test/lisp/emacs-lisp/package-resources/key.sec: Add new key.
* test/lisp/emacs-lisp/package-resources/signed/signed-good-1.0.el.sig:
* test/lisp/emacs-lisp/package-resources/signed/archive-contents.sig:
Update signatures using new key.