Identify extractable components in the multi-CTA `DeviceBatchedTopK` implementation

[elstehle]

The multi-CTA DeviceBatchedTopK currently sits at around 5k LOC. There are some components that qualify for being carved out into individual components.

The issue can be closed once we have sub-issues for the individual components that can be split out from the larger multi-CTA DeviceBatchedTopK implementation.