Fix NPE when using hinge split type without FoldingFeature

Before this CL, we only compute SplitType in getRelBounds.
However, we actually obtain the bounds to check minimum
dimensions in #computeSplitAttributes.

This CL moves the splitType calculation to
 #getPrimaryBounds and #getSecondaryBounds to cover the
minimum dimensions to fix NPE.

Test: atest ActivityEmbeddingBoundsTests
          on device without foldingFeature
Test: atest SplitPresenterTest
Bug: 263565586
Change-Id: Ibb826c25f072cdffd5b5adcd19571fe446d64f51