plugin code gets loaded outside of plugin host process

[akosyakov]

Plugin code gets bundled by webpack and loaded by node server process.

Plugin code loaded in the browser main process:

DialogsExtImpl bundled by webpack for the main browser process:

[akosyakov]

It also makes the bundling with webpack slower since it needs to load more unnecessary files. We have to sort it out.

[akosyakov]

@evidolob I think you are almost nailed it! I can see only 3 files are loaded:

If these files are reused in main process, maybe we should move them to common.

It would be good to have #5873 that it does not leak again.