fix(types): should wrap the top level setup refs with ShallowReactive

[KazariEX]

re-fix #12095

Expose IsShallowReactive to allow type inference in language tools.

In non-strict mode, undefined extends ShallowRef<infer V, unknown> will be inferred as true, causing UnwrapRef<undefined> to be inferred as unknown. Fix it here by the way.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB	38 kB	34.2 kB
vue.global.prod.js	159 kB	57.9 kB	51.4 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.9 kB	18.3 kB	16.7 kB
createApp	55 kB	21.3 kB	19.4 kB
createSSRApp	59 kB	23 kB	20.9 kB
defineCustomElement	59.8 kB	22.8 kB	20.8 kB
overall	68.7 kB	26.3 kB	24 kB

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commit: 3561e57