Generic method type parameter support

PR https://github.com/PowerShell/PowerShell/pull/12412#issuecomment-1023470022 introduced support for supplying type parameters to generic methods, e.g.:

```powershell
[Array]::Empty[int]()
```

While it kind of looks like it's already working (`[int]` is being highlighted the same way as `[Array]`) we should check for any edge cases and probably add some tests.