feat(terraform)!: require Terraform 1.5.6

[edersonbrilhante]

Description

Completes the repository-wide Terraform 1.5.6 minimum required by the compute-provider validation refactor. The EC2 provider introduced in #5251 already requires Terraform 1.5.6 for its provider-owned terraform_data validation; this PR raises the root module, examples, and all remaining internal modules to the same minimum.

Also aligns the Lambda MicroVM modules' AWS provider floor with the EC2 provider at >= 6.33.

Adds a TFLint suppression for the intentionally unused iam_overrides compatibility input in the multi-runner module.

This is a breaking change for users running Terraform 1.5.5 or older.

Test Plan

• Rebased the PR branch onto the latest main and verified the original commits were preserved with git range-diff.
• Verified the CI workflow files are absent from the final PR diff.
• Ran the repository pre-commit checks for Terraform formatting, TFLint validation, and merge-conflict checks.
• Verified the module versions.tf files and generated README requirement rows specify >= 1.5.6.
• Verified the Lambda MicroVM provider and trust-policy modules and generated documentation require AWS provider >= 6.33.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[Brend-Smits]

Reviewed and dev-deployed on a sandbox account.

This is a purely mechanical version-constraint bump (78 files, all README.md/versions.tf pairs raising required_version to >= 1.5.6), no functional/resource changes. All CI checks are green, and lambda unit tests pass (356/356). terraform plan against a live sandbox deployment shows zero infrastructure impact ("No changes. Your infrastructure matches the configuration."), as expected for a version-constraint-only change.

The breaking-change nature (Terraform <1.5.6 no longer supported) is clearly called out in the PR title/description. LGTM.