The term "tool" is historic from before the actual tool system got
introduced. Since then the term was already a bit confusing, because it
wasn't directly related to the tool system, but there was still some
relationship between the two. Now brushes and their types are decoupled
much more from the tool system, with a single "Brush" tool supporting
all kinds of brushes (draw, grab, cloth, smooth, ...).
For a more clear terminology, use "brush type" instead of "tool".
For #126032 we need to write the brush type to the asset metadata (done
in !124618), so we can filter brushes based on the type (so the grease
pencil eraser tool only shows eraser brushes, for example). I'd like to
use future proof names for that to avoid versioning of asset metadata in
future, so I'd rather do the full naming change now.
RNA properties (thus BPY names) are not changed for compatibility
reasons. Can be done in 5.0, see blender/blender#124201.
Pull Request: https://projects.blender.org/blender/blender/pulls/126796
a8c08e4a8c