ARM updates

What does this MR do?

Fixes a number of issues seen when running the playbook on ARM machines using tart.

• Homebrew path is changing from /usr/local to /opt/homebrew. There were a number of hardcoded references to this
• The dotnet Formula fails to build. Using the Cask for dotnet-sdk seems to work.
• The dotnet and powershell tests are failing. I've been asked to remove those tools entirely, but for now I'm only marking the tests as skipped. Will see if I have time to clean this up before going on leave. Ideally we'll keep the specs for the OSes where they are installed and working.
• Fix some issue running under tart and packer, which makes ansible add a lot of SSH keys to my agent, so making sure it uses password auth when asked.

Why was this MR needed?

Preparing for ARM support

What's the best way to test this MR?

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/ci-cd/shared-runners/macos/-/issues/20