Rename Packet references in the remaining places: code and config examples.

[ipochi]

Since #1537 was merged, it is slightly confusing to the end user that the documentation says Equinix Metal but in the code and cluster configuration we still continue to use packet.

This issue tracks the 2nd part of #1060.

Chiefly we should take care updating the following references:

1. Cluster config should be cluster "equinixmetal {}" instead of cluster "packet" {}
2. Examples, unit tests, CI should be changed to reflect the above point.
3. Migrate from Packet Terraform provider to Equinix Metal Terraform Provider
4. Migration steps for existing clusters.
5. Code changes {package names, build tags, file and dir names} from packet to equinixmetal
6. Packet CCM to EquinixMetal CCM
7. Any components making use of the reference packet be changed to equinixmetal
8. Configuration parameters to be updated to reflect the name change.