Refactors GitHub org management to orchestrated workflows

This commit introduces significant structural changes by implementing orchestrated GitHub Actions workflows for managing GitHub organization resources, ensuring consistency and dependency management. It moves from a simpler, parallel workflow to a more sophisticated one using orchestrator workflows and reusable components.

Changes

• Workflow Structure: Introduces orchestrator workflows (terragrunt-pr-orchestrator.yml, terragrunt-apply-orchestrator.yml) to manage resources in dependency order.
• Reusable Workflow Template: Creates a unified reusable workflow (terragrunt-unified-reusable.yml) to standardize actions across different resource types (org settings, members, teams, repositories). The common-env.yml is also introduced as a reusable workflow to setup environment variables.
• Template-Based Configuration: Implements HCL templates (_common/templates/*.hcl) for organization settings, members, teams, and repositories, providing reusable configuration patterns.
• Root Configuration: Adds a root.hcl to manage remote state and provider configuration.
• Pre-commit Hooks: Introduces .pre-commit-config.yaml and associated scripts (scripts/terragrunt-format.sh, scripts/terragrunt-format-check.sh) for formatting and linting HCL files before commit.
• Documentation Updates: Extensive documentation added in docs/ directory, covering configuration, workflows, environment variables, and GPG commit signing.
• Removes prior simple workflows: Deletes the prior single workflows terragrunt-apply.yml and terragrunt-pr.yml.

Impact

• Behavioral Changes: Enforces dependency order during application, validates changes in a structured manner, and introduces automated formatting checks via pre-commit hooks.
• Structural Changes: Major refactoring of the workflow system, moving from standalone workflows to an orchestrated, template-driven approach.
• Dependencies Affected: Relies on reusable workflows and templates, enforcing a consistent configuration style. Requires a GitHub token with organization admin permissions.
• Testing Implications: Requires thorough testing of orchestrated workflows, change detection logic, and template configurations. Emphasis is now on integration testing since individual steps are less meaningful.