Rename TU to Package Maintainer + Correct the ML url in bylaws

Hi,

I'm currently working on applying the rename of "Trusted User" to "Package Maintainer" which has been voted positively in this RFC (related ML thread here).

This MR aims to apply the rename ("Trusted User/TU" to "Package Maintainer") as well as correct the ML url in the bylaws (which hasn't been updated according to the migration to mailman3 yet)

Warning:
This MR implies the following task list to be done

• Rename this repo from "tu-bylaws" to "package-maintainer-bylaws" (to fit line 24 of the .gitlab-ci.yml and line 176 of the package-maintainer-bylaws.adoc) --> done by @klausenbusk
• Rename the dedicated url on AURweb from "https://aur.archlinux.org/tu/" to "https://aur.archlinux.org/package-maintainer/" --> Done by @moson, deployed by @artafinde
• Move the bylaw url to https://package-maintainer-bylaws.aur.archlinux.org and make the former one (https://tu-bylaws.aur.archlinux.org) redirect to it for while (while waiting for every references of this link to be updated). --> Done by @klausenbusk

Feel free to add tasks to the list if I missed any.

Related MRs/issues:

• Aurweb: aurweb!755 (merged)
• Infra: infrastructure#533