Reduce the number of choices to be made in Mac installation command lines

Step 2.7 of Mac installation is a bit crazy and you have to choose between different paths:

• Using “sudo” or not using “sudo”
• Using “disk” or “rdisk”
• Using “16m” or “16M”

We should:

• Check if “sudo” is needed on recent versions of macOS and use it by default if it’s the case.
• Use “rdisk” by default. For example using as placeholder only the number of the device (instead of /dev/disk[number]. Why would someone try the slow version first anyway?

Parent Task: #14548

Original created by @sajolida on 15124 (Redmine)