…ompatibility

This PR fixes the terragrunt module to properly handle TerragruntArgs and
TerraformArgs, and updates compatibility for Terragrunt v0.93.5+.

**Argument Handling:**
- Implement proper argument ordering: TerragruntArgs → --non-interactive → command → TerraformArgs
- Replace GetCommonOptions/GetArgsForCommand with buildTerragruntArgs() for consistent argument construction
- Remove deprecated -- separator approach that no longer works in newer Terragrunt versions

**v0.93.5 Compatibility:**
- Update command syntax from deprecated `run-all <cmd>` to new `<cmd> --all` format:
  - ApplyAll: `apply --all`
  - DestroyAll: `destroy --all`
  - PlanAllExitCode: `plan --all`

**Stack Commands:**
- Fix flag placement in stack output (-json flag now appears after command, not in TerragruntArgs)
- Fix --no-color flag format for proper parsing
- Add TerraformArgs support to stack commands

**Terragrunt Command Updates:**
- Add --non-interactive flag automatically for all Terragrunt commands (v0.93.5+)
- Remove terraform-specific flags (-input=false, -auto-approve) from TgApplyAllE and TgDestroyAllE
  that are not supported by Terragrunt run-all commands

**ValidateInputsE Function:**
- Update from deprecated `validate-inputs` to new `hcl validate --inputs` command (Terragrunt v0.88.1+)
- Update TestExtraArgsHelp to handle new command format in help output

- Update Terragrunt version from v0.80.4 to v0.93.5 in CircleCI config

Fixes #1609

Add comprehensive test coverage and documentation to complement the
TerragruntArgs/TerraformArgs fix.

**Test Enhancements:**
- Add unit tests for core cmd.go functions:
  - TestValidateOptions - validates option validation logic
  - TestBuildTerragruntArgs - table-driven tests for arg construction
  - TestPrepareOptions - tests default value setting
  - TestEnvVarsPropagation - verifies env vars are passed through

- Add E2E workflow tests in terragrunt_e2e_test.go:
  - TestTerragruntEndToEndIntegration - full Plan→Apply→Plan→Destroy workflow
  - TestStackEndToEndIntegration - stack Init→Generate→Run→Clean workflow

**Documentation:**
- Add README.md for terragrunt module with:
  - Requirements (Terragrunt + Terraform/OpenTofu)
  - How to specify terraform vs opentofu binary
  - Key concepts (Options, TerragruntArgs vs TerraformArgs)
  - Function reference (Stack vs Non-Stack)
  - Practical examples
  - List of unsupported terragrunt features
  - Compatibility notes

Test Coverage: All 38 tests pass, including new unit tests and E2E tests