fix(reactivity): handle `Set` with initial reactive values edge case

[shengxj1]

fix #8647

[github-actions[bot]]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB (+27 B)	37.9 kB (+8 B)	34.2 kB (-11 B)
vue.global.prod.js	158 kB (+27 B)	57.8 kB (+10 B)	51.4 kB (+6 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	47.2 kB (+27 B)	18.4 kB (+8 B)	16.8 kB (+49 B)
createApp	55.2 kB (+27 B)	21.4 kB (+10 B)	19.5 kB (+13 B)
createSSRApp	59.3 kB (+27 B)	23.1 kB (+9 B)	21 kB (+43 B)
defineCustomElement	60.1 kB (+29 B)	22.9 kB (+11 B)	20.9 kB (+11 B)
overall	69.1 kB (+27 B)	26.5 kB (+10 B)	24 kB (-46 B)

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commit: 129b9ee