Rename all Packet references to Equinix Metal

[johananl]

Packet was renamed to Equinix Metal lately. We should update any relevant references.

Things to consider:

• We might not want to break cluster "packet" {}. Maybe we should support both packet and equinix-metal for a while.
• We should verify we aren't breaking links.

[ahrkrak]

LGTM, I agree with supporting both.

[iaguis]

Let's rename documentation for now. It's fine to break links when renaming docs.

[invidian]

#1537 only partially addressed it.

[ipochi]

This issue has been partially fixed by addressing the documentation changes in #1537

Opened a new issue #1546 to track the code and config changes that are part of the PR #1545