re-enable extension checks for elemental and kubewarden in test-plugins-build

[aalves08]

Summary

Fixes #12026
Fixes #10995

• re-enable extension checks for elemental and kubewarden in test-plugins-build script since both projects have valid vue3 extensions in main and builds should work just fine
• adds extension check for neuvector extension

Occurred changes and/or fixed issues

Technical notes summary

Areas or cases that should be tested

Areas which could experience regressions

Screenshot/Video

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[cnotv]

LGTM