feat(multi-runner): integrate Lambda MicroVM provider

[edersonbrilhante]

Description

Integrates the Lambda MicroVM compute provider into the experimental multi-runner and runner-config contracts on top of #5260.

• Adds global and per-lane compute_provider.aws.microvm configuration and precedence resolution.
• Dispatches MicroVM lanes through runner-config while preserving the existing EC2 path.
• Adds MicroVM validation, outputs, documentation, and provider-aware runner-config tests.
• Keeps MicroVM lanes out of EC2 runner-binary synchronization.

Test Plan

• terraform -chdir=modules/multi-runner test -no-color -filter=tests/config-translation.tftest.hcl — 4 passed.
• terraform -chdir=modules/runner-config test -no-color — 24 passed.
• Full multi-runner testing reached the existing local Lambda ZIP fixture limitation; the relevant translation tests passed.
• terraform fmt, git diff --check, and pre-commit formatting/merge-conflict checks passed; TFLint reported only the unrelated existing iam_overrides warning.
• No live AWS deployment was performed.

Related Issues

• Depends on feat(microvm): add Terraform compute provider #5260.

[github-actions]

Dependency Review

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

Scanned Files

None