Use correct tsconfig.json in pure tests

This will change the pure tests Mocha setup to actually use the
`tsconfig.json` located in the `test` directory. Before, it was using
the root-level `tsconfig.json`. To ensure we are still using mostly the
same settings, this will extend the `test/tsconfig.json` from the
root-level `tsconfig.json`.

.vscode/launch.json

@@ -44,10 +44,8 @@
         "bdd",
         "--colors",
         "--diff",
-        "-r",
-        "ts-node/register",
-        "-r",
-        "test/mocha.setup.js",
+        "--config",
+        ".mocharc.json",
         "test/pure-tests/**/*.ts"
       ],
       "stopOnEntry": false,