22d30bc7da
Use `enum` type for the `filter_mode` parameter of many functions. This makes debugging easier and just makes the code slightly easier to understand. Also make the function parameter `const` wherever possible. Unfortunately, due to the `BEGIN_ANIMFILTER_SUBCHANNELS` and `END_ANIMFILTER_SUBCHANNELS` macros (which modify `filter_mode`), this is possible less often than I'd like. No functional changes. Pull Request: https://projects.blender.org/blender/blender/pulls/122882