Fix type inferencing and syntax highlighting for type variable with multiple bounds

Consider the following:
```groovy
class C<T extends Thread & Supplier<String>> {
  def m(T thread) {
    thread.get()
  }
}
```

"get" is shown as unknown (underlined).

![image](https://github.com/groovy/groovy-eclipse/assets/18193802/d8df8727-fb53-4bfd-b130-a2a1360d3360)
