feat: tgpu.fn(callback) for providing slots and accessors

[iwoplaza]

A new overload for tgpu.fn that accepts a shell-less callback and returns a callable that has a .with() method. This allows shell-less functions to also be provided with slot and accessor overrides.

Example

const countAccess = tgpu.accessor(d.f32);

const getDouble = () => {
  'use gpu';
  return countAccess.$ * 2;
};
// ^? () => number

const getDouble4 = tgpu.fn(getDouble).with(countAccess, 4);
//    ^? TgpuGenericFn<() => number>

const main = () => {
  'use gpu';
  return getDouble4(); // should return 8
};

Requirements

• If a shell-less function foo is used in code, and tgpu.fn(foo) is also used in code, it should only generate one definition.