fix(unplugin-typegpu): Babel plugin doesn't handle functions as object properties

[iwoplaza]

const DEFAULTS = {
  getGravity: () => {
    'use gpu';
    return d.vec3f(1, 2, 3);
  },
};

const main = () => {
  'use gpu';
  const hello = DEFAULTS.getGravity();
};

Allegedly, the babel plugin does not catch the getGravity function and doesn't emit metadata for it. Create a test case for both the rollup and babel version of the plugin, and fix the behavior if it occurs.