Similar to #104426, this adds a simple operator to set attribute values
for curves edit mode. The operator is very basic and is only meant to
be a first step for more attribute editing features. Some of the
functionality could be achieved with node tools, but without dynamic
socket types or access to the active attribute, it would be incomplete.
Some of the RNA property registration, retrieval, and setting is reused
from the mesh edit mode operator. The rest of the logic is similar but
harder to de-duplicate.
Pull Request: https://projects.blender.org/blender/blender/pulls/105076
31ec00895f