This commit renames the following DNA fields and corresponding RNA
properties to better represnt usage:
* `Brush.curve` to `Brush.curve_distance_falloff`
* `Brush.curve_preset` to `Brush.curve_distance_falloff_preset`
Pull Request: https://projects.blender.org/blender/blender/pulls/146254
This commit adds 9 tests that check each of the default brush curve
strength preset options to ensure that none of them cause NaN
propagation. In total this takes approximately 0.7s to run to run.
By design, these tests are very broad and are not a replacement for
other testing, but they should help in reducing the chance of potential
regressions.
Related to #140162
Pull Request: https://projects.blender.org/blender/blender/pulls/140242
