test(hypervisors): add unit tests for SPT

[r0hansaxena]

Description

Adds unit tests for the SPT VMM backend, covering BuildExecCmd and the interface methods (UsesKVM, SupportsSharedfs, Path, Ok, PreExec). Tests verify memory configuration, networking, block devices, extra monitor args and the binary not found error case.

Related issues

• Part of Add more unit tests #96

How was this tested?

All 13 unit tests pass locally. Full package tests pass. Linter passes (make lint, 0 issues).

LLM usage

LLM was used to assist with writing the tests. All code was reviewed and tested locally before submission.

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

[netlify]

✅ Deploy Preview for urunc canceled.

Name	Link
🔨 Latest commit	3c5086a
🔍 Latest deploy log	https://app.netlify.com/projects/urunc/deploys/69f8f37eeb2da70008d84a95