Skeleton retarget settings are lost when importing/reimporting a mesh with bone hierarchy changes

Importing a mesh that changes the hierarchy of a related skeleton causes the animation retarget settings on the skeleton to be lost. This is because in UInterchangeSkeletalMeshFactory::EndImportAsset_GameThread we call USkeleton::RecreateBoneTree which clears the bone tree on the skeleton, clearing the retarget settings.
Ideally, we would remap the retarget settings from the previous bone map to the new bone map so that bones that exist in both the old and new hierarchy retain their retarget settings

1. Import the attached MannequinRig_UE5.fbx to generate a SKM and Skeleton
2. Open the SKM asset in the mesh editor, go to the retarget settings and change the retarget settings for one of the bones
3. Now import the MannequinRig_UE5_ExtraSpineBones.fbx and target the Skeleton you just generated as the skeleton for this mesh
4. When prompted during the import, choose to regenerate the skeleton to account for the hierarchy changes. (Whether you propagate this to the other mesh - the second modal dialog popup - doesn't matter.)
5. After reimporting, open either of the SKMs and note that the retarget setting that you set previously is gone