Part 1, take 2: only partially remove unminify plugin

[davidsbailey]

Background

Reverts #30964, restoring #30831 which attempted to remove the UnminifyWebpackPlugin. The first attempt broke unit tests on the test machine (see #30964) because the exporter tests for applab and gamelab expect certain unminified files to exist in the webpack output under apps/build/package/js/. These passed on drone because drone does an unminified webpack build before running apps unit tests.

Description

This PR augments the initial attempt by reinstating UnminifyWebpackPlugin and limiting it to the files which are needed by the exporter tests.

Verification

Verified locally that the exporter tests fail after grunt clean, then pass again after yarn build:dist.

[islemaster]

Great diagnosis and fix. I'm glad the test machine caught this! Sorry I didn't remember it earlier.

One wonders if we should (in the future) do more to separate these "special case" bundles that we want to leave minified out from the rest of our pipeline - I imagine we don't want to do any automatic bundle splitting on them either.

[davidsbailey]

One wonders if we should (in the future) do more to separate these "special case" bundles that we want to leave minified out from the rest of our pipeline - I imagine we don't want to do any automatic bundle splitting on them either.

Good point -- we exclude these otherEntries from our explicit cacheGroups, but I am not sure they get excluded from the defaults. The defaults only affect on-demand chunks, which we don't have yet, but webpack may still be searching these giant entry points to look for them and may be doing other extra work too.