Build: Improve how combined assets are generated

Allows to revert changes applied in [54277] - temporary workaround for the failing Test NPM CI check on Windows.

Improvements included:
- generate combined asset files for both production and development
- store in the repository only the production version of the combined assets for packages, we use everything else only in development
- to make unit tests work, ensure that they ignore react fast refresh and use the production version of combined assets that are present in the source code

Props bernhard-reiter, jsnajdr, clorith, wildworks.
Fixes #56615.



git-svn-id: https://develop.svn.wordpress.org/trunk@54289 602fd350-edb4-49c9-b593-d223f7449a82

.github/workflows/test-npm.yml

@@ -55,7 +55,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 20
     if: ${{ github.repository == 'WordPress/wordpress-develop' || github.event_name == 'pull_request' }}
-    continue-on-error: ${{ matrix.os == 'windows-latest' }}
     strategy:
       fail-fast: false
       matrix: