Root motion extraction fails on blendspaces with bShouldMatchSyncPhases set

There’s a bug with the bShouldMatchSyncPhases codepath in UBlendSpace::TickAssetPlayer. That codepath calls ResetBlendSamples to give a deterministic output when advancing time on the animations owned by the blendspace. But this also resets FBlendSampleData::PreviousTime on all the sampled animations, which means we have no delta time when it comes to calculating root motion.

1. Open Anim Sandbox
2. Create a blendspace asset
3. Drop in a few locomotion assets that contain root motion (eg. M_Neutral_Run_Loop_F, etc)
   1. Setup the animations within the blendspace
4. In the blend space viewport, turn on preview of root motion (Animation > Root Motion > Loop)
   1. Expected behaviour: the root motion moves the character in the level viewport
   2. Actual behaviour: very little or no root motion is applied to the character