Adds support for generics in`derive-impl` (#5584)

As raised by @Kianenigma

 in
https://github.com/sam0x17/macro_magic/issues/15, this PR adds the
support for generics while using `derive_impl`.

This can then be used in conjunction with `FliteFrameSystem` being
defined [here](https://github.com/kianenigma/flite) as
```diff
+#[derive_impl(FliteFrameSystem<Configuration>)]
impl frame_system::Config for Runtime {
  type Block = Block;

  // .. Rest can be removed
}
```

---------

Co-authored-by: Kian Paimani <[email protected]>