…polation time

The lerp smoothing pass used by the Lerp and SmoothDampening interpolation
types applied a fixed factor of 1.0 minus the maximum interpolation time once
per frame, with no delta time. The wall clock smoothing rate therefore scaled
with the frame rate, so the same setting smoothed by different amounts on
different hardware. The factor is now raised to the number of 60fps reference
frames elapsed, which makes the rate a function of elapsed time. Results at
60fps are unchanged for every legal setting.

Separately, a maximum interpolation time of 1.0 (the upper bound of the
inspector range) produced a factor of exactly 0, so the interpolated value
never advanced and the transform stopped moving entirely on all three axes.
The retained portion is now clamped just below 1.0. This is an independent
defect, as raising 1.0 to any power is still 1.0.

The LegacyLerp path was already frame rate correct and is unchanged. The
documentation on the lerp smoothing fields described the LegacyLerp formula
for all interpolation types and has been corrected.

…merate-up-port

…-port

…-port