The previous way of considering tools with the `data_block` member set
as using brushes was rather unclear/confusing, but also a bit outdated
with the brush assets changes. Since then most sculpt/paint modes use a
unified brush tool, there was no tool for every brush type (aka brush
tool) anymore. So now the `data_block` member was just set dynamically to
match the active brush type which is otherwise irrelevant to the tool
system now.
Further, this will become important to bring back some of the tools that
use brushes in grease pencil draw mode, see #116337. For that we want to
keep the unified brush tool, but still allow other tools that only use a
specific brush type. So marking a tool as using brushes should be done
separately from indicating a specific brush type.
Removing/replacing the `data_block` member should happen separately
still, pending further developments (e.g. see #125449).
Pull Request: https://projects.blender.org/blender/blender/pulls/125911
b64bf66257