feat!: Central CI for TF

[MichaelThamm]

Fixes canonical/observability-stack#39

Sample implementation:

• feat: TF CI alertmanager-k8s-operator#350

TODO:

• Determine how to deduplicate the TF CI between _charm-quality-checks.yaml and _charm_-terraform.yaml
• Implement recommendations

Warning

If merged, this will make its way into the v2 track tag, meaning that all charms repo PRs which have .tf file changes will need to conform to the Terraform CI standard. This includes having:

1. justfile
2. .tfdocs-config.yml

Without this, PRs will need to be merged on failing TF CI, which is not blocking.

This PR also introduces a linting check which ensures that the endpoints in the outputs.tf file is up-to-date with the charmcraft.yaml. E.g. In the alertmanager-k8s repo you can see we are already diverging:

❯ just lint-tf-endpoints
service-mesh is missing from endpoints
require-cmr-mesh is missing from endpoints
provide-cmr-mesh is missing from endpoints
error: Recipe `lint-tf-endpoints` failed with exit code 1