Adding pull request and main push acceptance tests runner

[mawasile]

This pull request includes several updates to Terraform configurations, GitHub workflows, and internal package structures. The changes enhance provider configurations, improve testing workflows, and refactor internal package naming for better clarity and maintainability.

Terraform Configuration Updates:

• Added azurecaf and azurerm providers in .devcontainer/features/acceptance_test_dependencies/main.tf and docs/resources/billing_policy_environment.md. [1] [2]
• Removed version constraints from azurerm and azurecaf providers in docs/resources/billing_policy.md and examples/resources/powerplatform_billing_policy/resource.tf. [1] [2]

GitHub Workflow Enhancements:

• Added pull_request trigger and updated paths for push trigger in .github/workflows/run_tests.yml.
• Commented out the unit_test job and enhanced the acceptance_test job to include Terraform setup and local provider installation in .github/workflows/run_tests.yml. [1] [2]
• Updated go test commands to include go clean -testcache and -failfast options in .github/workflows/terraform_provider.yml. [1] [2]

Internal Package Refactoring:

• Renamed internal packages from powerplatform to api in several files (api_client.go, auth.go, lifecycle.go, request.go). [1] [2] [3] [4]
• Moved constants package to internal/powerplatform/constants and renamed it for better clarity. [1] [2]

Error Handling and Logging Improvements:

• Enhanced error handling in ExecuteForGivenScope and doRequest methods in internal/powerplatform/api/api_client.go and request.go. [1] [2]
• Added retry logic with context timeout in Execute method in internal/powerplatform/api/api_client.go.

These changes collectively improve the maintainability, reliability, and clarity of the codebase, while also enhancing the CI/CD workflows to better handle Terraform provider dependencies and testing.