Create an e2e test for state patching

[tillrohrmann]

restatedev/restate#1486 discovered that our state patching feature does not work. Apparently, we don't have enough test coverage for this feature (none) because otherwise, we would have caught the problem. It would be great to add a simple state patching e2e test.

The original issue that introduced this feature is restatedev/restate#1061.