Incorrect order of imports in the chunk when using dynamic imports and code splitting

[web-padawan]

Potentially related to #399 or #2983 - if so, feel free to close as duplicate.

Here is the reproduction. Run npm i && npm run build && npm start and check the console.

The issue manifests when having two dynamic imports in src/app-element.js (with static imports, everything works fine).

Content of imported files

• @vaadin/checkbox/vaadin-checkbox.js

import './theme/lumo/vaadin-checkbox.js';
export * from './src/vaadin-checkbox.js';

• @vaadin/checkbox/theme/lumo/vaadin-checkbox.js

import './vaadin-checkbox-styles.js'; // order of these two imports matters
import '../../src/vaadin-checkbox.js';

• @vaadin/checkbox-group/vaadin-checkbox-group.js

import './theme/lumo/vaadin-checkbox-group.js';
export * from './src/vaadin-checkbox-group.js';

• @vaadin/checkbox-group/theme/lumo/vaadin-checkbox-group.js

import '@vaadin/checkbox/theme/lumo/vaadin-checkbox.js';
import './vaadin-checkbox-group-styles.js';
import '../../src/vaadin-checkbox-group.js';

The underlying logic used by these web components assumes that theme files end up in the bundle before src files.
When using static imports, this works as expected and the output of files in the bundle matches the order of imports:

// node_modules/@vaadin/checkbox/theme/lumo/vaadin-checkbox-styles.js
// node_modules/@vaadin/checkbox/src/vaadin-checkbox-mixin.js
// node_modules/@vaadin/checkbox/src/vaadin-checkbox-styles.js
// node_modules/@vaadin/checkbox/src/vaadin-checkbox.js

However, when using dynamic imports and code splitting, file from theme folder is bundled after the src files:

// node_modules/@vaadin/checkbox/src/vaadin-checkbox-mixin.js
// node_modules/@vaadin/checkbox/src/vaadin-checkbox-styles.js
// node_modules/@vaadin/checkbox/src/vaadin-checkbox.js
// node_modules/@vaadin/checkbox/theme/lumo/vaadin-checkbox-styles.js