Make wasm-opt mandatory for Releases

[holgerd77]

The wasm-opt Rust package is marked as optional - see here in the Rust build script - and build is also running if the package is not installed.

This is suboptimal since this bears the risk of doing releases without the optimization step. This should especially be avoided since - if we merge things to master on the monorepo side, this library will get published within the realm of our normal library stack.

So we should either make this mandatory by default in general or alternatively add a check later in the pipeline (when doing releases e.g., with a pre-publish hook or something?).