Change to using CompactTensorV2 as default impl for sparse tensors.
Change to using CompactTensorV2 as default impl for sparse tensors.

vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa