Add a quaternion attribute type that will be used in combination with
rotation sockets for geometry nodes to give a more intuitive experience
and better performance when using rotations.
The most interesting part is probably the interpolation, the rest is
the same as the last attribute type addition, 988f23cec3.
We need to interpolate multiple values with different weights.
Based on Sybren's suggestion, this uses the `expmap` methods from
4805a54525 for that.
This also refactors `SimpleMixerWithAccumulationType` to use a
function rather than a cast to convert to the accumulation type.
See #92967
Pull Request: https://projects.blender.org/blender/blender/pulls/108678
1e4b80fed9