chore(vscode): use `unjs/unbuild` for bundling

[KermanX]

Use https://github.com/unjs/unbuild to bundle the VSCode extension, also as a preparation for #4994.

Notes:

• To dev the extension: run pnpm dev:vue, the command will exit after the stub files generated (no need to watch file changes), then F5.
• To build the extension: like before.
• Other packages except the VSCode extension remain unchanged.
• Using sonda for package size reporting.

TODOs:

• Should the tasks defined in .vscode/tasks.json and .vscode/launch.json be restored?
• What is node_modules/vue-typescript-plugin-pack/ used for?

[pkg-pr-new[bot]]

Open in Stackblitz

vue-component-meta

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-meta@4998 ```

vue-component-type-helpers

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-component-type-helpers@4998 ```

@vue/language-plugin-pug

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-plugin-pug@4998 ```

@vue/language-core

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-core@4998 ```

@vue/language-server

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-server@4998 ```

@vue/language-service

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/language-service@4998 ```

vue-tsc

``` pnpm add https://pkg.pr.new/vuejs/language-tools/vue-tsc@4998 ```

@vue/typescript-plugin

``` pnpm add https://pkg.pr.new/vuejs/language-tools/@vue/typescript-plugin@4998 ```

commit: 13daf63