Unity 2021.3.17f1 spams line ending warnings when loading the built Cesium for Unity

For example:

```
There are inconsistent line endings in the 'Packages/com.cesium.unity/Editor/generated/Reinterop/Reinterop.RoslynSourceGenerator/CesiumIonSession-generated.cs' script. Some are Mac OS X (UNIX) and some are Windows.
This might lead to incorrect line numbers in stacktraces and compiler errors. Many text editors can fix this using Convert Line Endings menu commands.
```

This happens because we generate code on different platforms, and then smash them together with ifdefs. We should normalize the line endings as part of the build process.