fix(compiler-core): change v-for key type to match Object.keys

[ferreraa]

close #8819

When using v-for with an object of type T, the type assigned to the item keys is keyof T.
Since TS 2.9, calling keyof {[key: string]: any} produces a type string | number.

Behind the scenes, vue calls the Object.keys method to produce the keys when using v-for. (see L.81 of renderList.ts)
Object.keys's return type being string[], it sometimes creates a difference between the actual type of the key and the type assigned by vue.

One could argue that keyof is able to provide stricter typing of the keys in some other cases but microsoft deliberately took the decision of typing Object.keys that way and doing differently would only induce more confusion.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	90.7 kB	34.5 kB	31.1 kB
vue.global.prod.js	148 kB	53.7 kB	48 kB

Usages

Name	Size	Gzip	Brotli
createApp	50.8 kB	19.9 kB	18.1 kB
createSSRApp	54.1 kB	21.2 kB	19.3 kB
defineCustomElement	53.1 kB	20.6 kB	18.8 kB
overall	64.5 kB	24.9 kB	22.6 kB

[sodatea]

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[vue-bot]

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vue-simple-compiler	✅ success	✅ success