Use thread-loader for heavy loaders

What does this MR do and why?

This MR improves frontend building performance by using thread-loader for resource heavy webpack loaders.

This change improves compilation times in our CI with sourcemaps disabled in another MR.

Note: we're using a single worker because our CI runners provide 2 cores only.

Performance comparison

The yarn run webpack-prod command testing has been conducted with NO_SOURCEMAPS=true environment variable which disabled source maps generation.

Before	After
558.79s	490.76s

How to set up and validate locally

1. Run NO_SOURCEMAPS=true yarn run webpack-prod