wasm-opt flags -Os vs. -Oz

Locally I'm testing the two optimization modes with wasm-opt version 110:

```
$ wasm-opt --help
…
-Os execute default optimization
passes, focusing on code size

-Oz execute default optimization
passes, super-focusing on code
size
…
```

For my tests, there is a difference in the order of magnitute of 1-2%:

```
# -Os

-rwxr-xr-x 1 me staff 192130 16 Okt 17:27 nois_demo.wasm
-rwxr-xr-x 1 me staff 480903 16 Okt 17:27 nois_oracle.wasm
-rwxr-xr-x 1 me staff 225705 16 Okt 17:27 nois_proxy.wasm

# -Oz

-rwxr-xr-x 1 me staff 189263 16 Okt 17:29 nois_demo.wasm
-rwxr-xr-x 1 me staff 472586 16 Okt 17:29 nois_oracle.wasm
-rwxr-xr-x 1 me staff 223632 16 Okt 17:29 nois_proxy.wasm
```

So for now I don't see a strong need to move away from the well established `-Os`.