Improve .NET install on Linux docs

[noahfalk]

Describe the issue or suggestion

In the packages section of this page I was trying to install .NET on Azure Linux and found the text confusing in two ways:

1. The doc says packages exist for Azure Linux, but it doesn't tell me what the naming convention is or what package manager app to run. All the other distros link to distro-specific pages that provide example command-lines. I now know the answer for Azure Linux is 'tdnf install dotnet-sdk-X.0" but I didn't know that the first time I was reading those docs.

2. The top section is now labeled "Packages are available for the following Linux distributions" which sounds like distros not in that top list of 4 don't have packages? Could we put all nine distros in a single list and leave the information about who publishes the packages/what repo the packages are in on the distro-specific instructions page?

cc @richlander