Improve module validation performance

[seanmil]

Validate that each module exists only once, as that module is being processed.

Summary

During module cloning, the module validation function is called for all modules on each iteration through the module list, resulting in the cloning taking much longer than it needs to.

This change adjusts the code to validate one module at a time as that module is being processed.

Checklist

• [x] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [x] Manually verified.

[CLAassistant]

All committers have signed the CLA.

[jordanbreen28]

Pulled and manually verified! Thanks again @seanmil!