Cleanup zip.js configuration to use one file in Source/Core/

After https://github.com/CesiumGS/cesium/pull/9861 gets merged, we should clean up the calls to `zip.configure()` so we only have to do it once. 1ff47b6 has a first pass at doing this with an extra file in Source/Core/ that calls `configure` and re-exports zip.js, but this does not work when CesiumJS is built. Another approach could be to write a function in the Source/Core/ file that returns the zip.js module itself after calling `configure`.

Review the zip.configure() call sites in Source/Core/ and the first-pass approach from commit 1ff47b6. Run a CesiumJS build to reproduce why the extra Source/Core/ file and re-export do not work, then verify that zip.js is configured once and remains usable throughout the build.

Written by the indexing model from the issue text.