upgrade terraform to opentofu 1.6.4, switch to s3 backends
This upgrades Terraform to OpenTofu 1.6.4. As Terraform deprecated the Swift backend, this changes to S3 using the same bucket.
This also changes the workflow for Terraform usage in overcloud, here are the instructions:
cd overcloud
# Create ec2 credentials with openstack CLI
openstack ec2 credentials create
# Load the credentials in your environment
source ./get_terraform_credentials.sh
# Do your Terraform stuff
# ...
# When you're done:
unset AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY