Multipass setup instructions do not work on Mac with M1 silicon

https://github.com/cloud-native-toolkit/automation-solutions/blob/main/common-files/RUNTIMES.md

I hit some problems with the steps to setup Multipass on Mac:

1. The command `multipass mount $PWD cli-tools:/automation` failed. This was because the VM did not have access to the internet, and could not install an OS repository with snap. On Mac, I needed to disable the firewall setting 'Stealth Mode' to get this to work (System Preferences->Firewall Tab->Firewall Options)

2. The command `multipass launch --name cli-tools --cloud-init ./cli-tools.yaml` installed the incorrect AMD binaries which will not run with an M1 chip. This is because the command `uname -m` inside the VM returns `aarch64`, not 'arm64' as expected by the cli-tools.yaml.