Minimize `main.jar` and `bootstrap.jar` for release builds

[chippmann]

I just found this: https://imperceptiblethoughts.com/shadow/configuration/minimizing/

We don't use this atm. But it should be easy to use minimization for release builds.

[piiertho]

I wonder if we would encounter side effect with graal native-image. I think it should be ok, but we should test.