Simplify the Distribution Matrix for Linux Installers.

#499 kicked off a fun discussion in the PMC:

In essence, it isn't feasible for us to support the proliferation of Linux Distributions. However, we can through tooling and documentation make sure that folks who use a Linux distribution can easily install our packages.

As an example for Red Hat based distribution in our `linux/Jenkinsfile` we have something like:

```
'redhat' : [
'rpm/centos/7',
'rpm/rocky/8',
'rpm/rhel/7',
'rpm/rhel/8',
'rpm/rhel/9',
'rpm/fedora/35',
'rpm/fedora/36',
'rpm/oraclelinux/8',
'rpm/amazonlinux/2',
'rpm/oraclelinux/7'
],
```

Current thinking is to:

1. _symlink_ everything that isn't rpm/rhel/ to their equivalent rpm/rhel/ to retain existing compatibility.

2. Update the website documentation on how to use the `rpm/rhel/` for a user's specific Linux distro. This would include not "don't recommend the specific distro name", but use correct `rhel/` instead, and provide a mapping table.

e.g. If you're using Fedora 36 then that maps to rhel version 8 (or whatever)

_Originally posted by @karianna in https://github.com/adoptium/installer/issues/499#issuecomment-1183208458_