[Tracker] Pending items for NN Descent

[divyegala]

• Consolidate code in cuVS by migrating over diff of features from RAFT
• Triage CI wheel test failures
• Triage batch test failures
• Add mutual reachability API and triage HDBSCAN numerical instabilities when using NN Descent ([FEA] Enable HDBSCAN to build knn graph using NN Descent cuml#5939)
• Additional distances
• For float16 input, make sure data is not copied if it's already on device
• indices are returned on host and distances on device. Return both in the same location and let user choose