Generate argument code for TGSL functions based on the shell, not on the AST.

[iwoplaza]

Currently, resolving the following function will generate a WGSL function with no arguments:

tgpu
  .fn([d.arrayOf(d.f32, gridSize)])
  .does(() => {
    // do something
  })
  .$name('fill');

That's because the arguments are based on what's in the AST, and not what's in the shell.
Arguments omitted from the AST should be given unique but random names, like param_0, param_1, etc...