For gradients with fill spread set as repeat,
the lack of anti-aliasing between the last and
the first color caused noticeable jagged edges.
Interpolation was introduced between them,
visually improving the gradient quality.
Rather than aiming for extremely high accuracy,
a compromise can achieve with better performance.
This modification helps prevent unnecessary image rotation.
issue: https://github.com/thorvg/thorvg/issues/2265
sw_engine: radial gradient
[issues 2014: radial gradient](#2014)
Radial gradient results in a corrupted image when the focal point is outside the circle on Apple Silicon.
This happens because some compilers use FMA to optimize the a = dr² - dx² - dy² calculation,
which cause loss of precision.
We rely on temporary variables to prevent FMA.
We could also use compiler specific float contraction control pragmas to avoid this if this doesn't work in the future
