fix: Duplicate values during deep assign of extra files

[mmaietta]

Follow up from: #6841 (comment)

Filters out duplicate assign's when cascading configs (files, extraFiles, etc.) by converting to Set first

[changeset-bot]

🦋 Changeset detected

Latest commit: 7d89692

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 10 packages

Name	Type
builder-util	Patch
app-builder-lib	Patch
dmg-builder	Patch
electron-builder-squirrel-windows	Patch
electron-builder	Patch
electron-publish	Patch
electron-forge-maker-appimage	Patch
electron-forge-maker-nsis-web	Patch
electron-forge-maker-nsis	Patch
electron-forge-maker-snap	Patch

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