Refactored how CMake passes version & settings info

- keys can now be passed per-build passing -DLAIKA_PUBKEY=[pubkey] & -LAIKA_PRIVKEY=[pubkey] to `cmake -B`
- if those definitions aren't passed, the default public & private key will be used (for quick testing)

.vscode/settings.json

@@ -23,7 +23,8 @@
         "variant": "cpp",
         "stdio.h": "c",
         "bit": "c",
-        "limits": "c"
+        "limits": "c",
+        "*.in": "cpp"
     },
     "cSpell.words": [
         "CWARN",