feat(language-core): enhance single root nodes collection

[KazariEX]

This is an enhancement which enabling it to collect all single root nodes under the template branch, and selectively collect single root child node through specific components.

It will also infer the type of $el as the union of all single root nodes.

[pkg-pr-new]

Open in Stackblitz

vue-component-meta

pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-meta@4819

vue-component-type-helpers

pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-type-helpers@4819

@vue/language-core

pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-core@4819

@vue/language-plugin-pug

pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-plugin-pug@4819

@vue/language-service

pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-service@4819

@vue/language-server

pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-server@4819

vue-tsc

pnpm add https://pkg.pr.new/vuejs/language-tools/vue-tsc@4819

@vue/typescript-plugin

pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/typescript-plugin@4819

commit: f1f5c2f