chore(terraform): align with current terraform standards (charmkeeper)

[seb4stien]

This PR fixes all 6 Terraform modules in dns-operators to align with current standards.

Modules updated

• terraform/ (product module)
• bind-operator/terraform/
• dns-integrator-operator/terraform/
• dns-policy-operator/terraform/
• dns-resolver-operator/terraform/
• dns-secondary-operator/terraform/

Changes

• Fix Terraform required_version: >= 1.6 → ~> 1.12 in all 6 modules
• Fix Juju provider version: >= 1.0.0 → ~> 1.0 in all 6 modules
• Enable terraform_required_version tflint rule in all 5 operator modules (was false)
• Add missing .tflint.hcl to product terraform/ module
• Add terraform/tests/ (setup + test) to all 6 modules (all use lxd-controller, machine charms)
  • bind rev 80, dns-integrator rev 2, dns-policy rev 2, dns-resolver rev 1, dns-secondary rev 2
• Replace partial test_terraform_files.yaml with full test_terraform_modules.yaml covering all 6 modules with terraform test
• Update renovate.json: add CharmHub datasource, regex manager, ignorePaths: []

Automated by charmkeeper

[seb4stien]

I mark this one as "blocked" as I shouldn't merge it. It would be better to get it merged (if relevant) by someone working on the charm as it may require a redeployment to staging afterwards.