brew: install correctly on apple silicon

[damonbreeden]

brew expects to see files in /opt/homebrew on Apple silicon so check for that and set the paths accordingly

[TheKevJames]

Looks great to me! Thanks for tackling this. :)

[sp-ricard-valverde]

Late to the party, but seems that $::facts[processors][models] is not always available.
I've found the issue when running on GitHub CI macOS workers but I can reproduce the same locally(processor fact has no modules key)

[TheKevJames]

@sp-ricard-valverde shoot. Anything special about those systems? Or perhaps any other keys in processor we might be able to fall back to checking?

[sp-ricard-valverde]

Nothing special that I could see. It may be related to OS permissions, Full Disk Access, ... dunno.
I ended up successfully implementing the has_arm64 fact from PR #154 as processors did not contain relevant information.
There are already facts regarding architecture though(with values x86_64, arm64) that seem to be pretty reliable.