This new discontinuity filter performs actions on the entire Euler rotation, rather than on the individual X/Y/Z channels only. This should make it fix a wider range of discontinuities, for example those in {T52744}.
This first review pass is to get feedback from animators on the functionality, so ignore the code for now.
**Test builds:**
* [Linux](https://builder.blender.org/download/temp-T52744-euler-filter/temp-T52744-euler-filter-blender-2.92.0-4fd2a465544b-linux64.tar.xz)
* [Windows](https://builder.blender.org/download/temp-T52744-euler-filter/temp-T52744-euler-filter-blender-2.92.0-4fd2a465544b-windows64.zip)
* [macOS](https://builder.blender.org/download/temp-T52744-euler-filter/temp-T52744-euler-filter-blender-2.92.0-4fd2a465544b-macOS.dmg)