fix(runtime-core): avoid rendering plain object as VNode

[edison1105]

close #12035
close vitejs/vite-plugin-vue#353

I initially planned to fix this in @vue/babel-plugin-jsx like this. However, I encountered this scenario during the process. It might require introducing additional runtime checks to determine whether the child is a VNode or an Object. Doing so could lead to some performance loss, so I abandoned this approach.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB (-13 B)	38 kB	34.2 kB (-28 B)
vue.global.prod.js	160 kB (-13 B)	58 kB (-1 B)	51.6 kB (+69 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	49 kB (+10 B)	18.9 kB	17.3 kB (+46 B)
createApp	55.6 kB (+10 B)	21.4 kB (+7 B)	19.5 kB (-22 B)
createSSRApp	59.6 kB (+10 B)	23.1 kB (+4 B)	21 kB (+48 B)
defineCustomElement	60.4 kB (+10 B)	23 kB (+7 B)	20.9 kB (+6 B)
overall	69.3 kB (-13 B)	26.5 kB (-1 B)	24.1 kB (+59 B)

[pkg-pr-new]

Open in Stackblitz

@vue/compiler-dom

pnpm add https://pkg.pr.new/@vue/compiler-dom@12038

@vue/compiler-core

pnpm add https://pkg.pr.new/@vue/compiler-core@12038

@vue/compiler-sfc

pnpm add https://pkg.pr.new/@vue/compiler-sfc@12038

@vue/compiler-ssr

pnpm add https://pkg.pr.new/@vue/compiler-ssr@12038

@vue/reactivity

pnpm add https://pkg.pr.new/@vue/reactivity@12038

@vue/runtime-dom

pnpm add https://pkg.pr.new/@vue/runtime-dom@12038

@vue/runtime-core

pnpm add https://pkg.pr.new/@vue/runtime-core@12038

@vue/server-renderer

pnpm add https://pkg.pr.new/@vue/server-renderer@12038

@vue/shared

pnpm add https://pkg.pr.new/@vue/shared@12038

vue

pnpm add https://pkg.pr.new/vue@12038

@vue/compat

pnpm add https://pkg.pr.new/@vue/compat@12038

commit: 0574815

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
nuxt	✅ success	✅ success
pinia	✅ success	✅ success
primevue	✅ success	✅ success
quasar	✅ success	✅ success
radix-vue	✅ success	✅ success
router	✅ success	✅ success
test-utils	✅ success	✅ success
vant	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vue-macros	✅ success	✅ success
vuetify	✅ success	✅ success
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success