feat(hashicorp/terraform): add terraform provider

[gnmsa]

Description

Adds a new POSH provider for HashiCorp Terraform.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 💥 Breaking change
• 📝 Documentation
• ♻️ Refactoring
• ⚡ Performance
• ✅ Tests
• 🔧 Build/CI

Related Issue

Changes

• Command with subcommands: init, plan, apply, destroy, workspace, output, state
• Config supporting workspace paths, Azure backend config (resource group, storage account, container), and service principal credentials
• JSON schema for config validation (config.schema.json, config.base.json)
• Updates posh.schema.json with terraform config definitions

Checklist

• My code adheres to the coding and style guidelines of the project.
• I have performed a self-review of my own code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.