fix(ssr): properly init slots during ssr rendering

[edison1105]

close #12438

during SSR rendering, the optimized parameter passed to initSlots is always false. The slots._ flag is lost when initSlots is called in setupComponent for the child component. This triggers the logic inside normalizeObjectSlots, resulting in slotFn returning an array that includes a comment node.

core/packages/server-renderer/src/helpers/ssrRenderSlot.ts

Lines 59 to 65 in 413c923

	const ret = slotFn(
	slotProps,
	bufferedPush,
	parentComponent,
	slotScopeId ? ' ' + slotScopeId : '',
	)
	if (isArray(ret)) {

related commit 3d34f40#diff-56930a63772d2e89f19432918b9d6ed851ede4159b0d32404e0c1d8c159fec99R1232
SSR rendering does not need to patch slots, so there won't be an issue similar to #10870. Perhaps the optimized parameter can always be set to true.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB (+3 B)	37.9 kB (-1 B)	34.2 kB (-2 B)
vue.global.prod.js	158 kB (+3 B)	57.8 kB (+3 B)	51.5 kB (+99 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	47.2 kB (+3 B)	18.3 kB (+2 B)	16.8 kB (-3 B)
createApp	55.2 kB (+3 B)	21.3 kB (+2 B)	19.5 kB (-6 B)
createSSRApp	59.3 kB (+3 B)	23.1 kB (+4 B)	21 kB (+1 B)
defineCustomElement	60.1 kB (+3 B)	22.9 kB (+3 B)	20.9 kB (+3 B)
overall	69.1 kB (+3 B)	26.5 kB (+2 B)	24.1 kB (+15 B)

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commit: 413c923

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