draft: bin: Replace gen_release_notes with pre_release script

Add full pre- and post- release scripts, which in conjunction with xorg/util/modular!19, allows the release script to automatically handle many of the pre- and post- release tasks in the repo automatically. This includes generating docs, updating the release calendar, updating the version number, etc.

Most of this works fine, but there are some issues with the ported release script itself that need to be worked out.