Prevent name prefix length error for bigquery

[adatzer]

With bigquery default pipeline, when prefix is more than 6 characters long, terraform plan errors with:

│ Error: "name_prefix" cannot be longer than 37 characters, name is limited to 63
│ 
│   with module.bigquery_loader[0].google_compute_instance_template.tpl["streamloader"],
│   on .terraform/modules/bigquery_loader/main.tf line 309, in resource "google_compute_instance_template" "tpl":
│  309:   name_prefix = "${var.name}-${each.key}-"

Info to reproduce:

• On Terraform 1.3.0
• On gcp/pipeline/default
• In bigquery.terraform.tfvars supply a prefix with a value more than 6 chars long,e.g. testersp
• terraform init and terraform plan -var-file=bigquery.terraform.tfvars