fix: apply default origin to plugins provided by plugin detection

[pieh]

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Summary

Part of https://linear.app/netlify/issue/FRP-1218/plugin-netlifyplugin-nextjs-must-not-be-specified-twice-in-the-app

We are setting default origin for build command and publish dir, but not for plugins we set from plugin detection - this makes that all setting provided by plugin detection has corresponding origin property set. See netlify/build#5793 on how added origin actually fixes the issue

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[github-actions]

📊 Benchmark results

Comparing with 7751edc

• Dependency count: 1,222 (no change)
• Package size: 313 MB ⬇️ 0.00% decrease vs. 7751edc
• Number of ts-expect-error directives: 977 (no change)

[lukasholzer]

Oh that's a great addition!