[XLA:GPU] Minor refactoring to cleanup argument passing in `conv_algorithm_picker`.
[XLA:GPU] Minor refactoring to cleanup argument passing in `conv_algorithm_picker`.

The `PickBest...` methods have more arguments that necessary. This change removes the unnecessary arguments, pushing some logic to leaf methods. This makes the top level `PickBestAlgorithmNoCache` simpler and symmetrical when it comes to the different platforms.
