Feature Request Dont unparent kinematic rigidbodies

Kinematic child rigidbodies are necessary for building hitzones or moving sub colliders (e.g. car doors).
It took us a long time to figure out that the solution is just to reparent the sub rigidbodies which is also tricky because unparenting seems to take place at the end of the conversion pipeline.

Right now we need to use a "hack" that runs a system once at runtime to reparent the rb.

In contrast to dynamic rigidbodies, kinematic rigidbodies should not be unparented by default.

Here is a discord thread on this topic for further information: https://discord.com/channels/489222168727519232/1050513998078021634