Test height query extrapolation

[huwb]

Status: Not ready to merge but is probably a reasonable approach. Should obviously have all the data reverted.

@EliGould this adds a new object "Sphere" to main.unity and it has a height probe viualisation, and an option added to OceanHeightDemo for extrapolating forwards in time to compensate for query latency. On my laptop and it reduces the 'lag' noticeably. Hopefully it holds up for higher latency too.