Closes https://github.com/ppy/osu/issues/25239.
`LegacyEditorBeatmapPatcher.processHitObjectLocalData()` was already
supposed to be handling changes to hitobjects that will show up neither
when comparing the hitobjects themselves or the timing point with
"legacy" info stripped - so, in other words, changes to slider velocity
and samples.
However, a change to slider velocity requires default application to
take effect, so just resetting the value would visually fix the timeline
marker but not change the actual object. Calling
`EditorBeatmap.Update()` fixes this by way of triggering default
re-application.
This could probably be smarter (by only invoking the update when
strictly necessary, etc.) - but I'm not sure it's worth the hassle. This
is intended to be a quick fix, rather than a complete solution - the
complete solution would indeed likely entail a wholesale restructuring
of the editor's change handling.
Previously, all control points would get replaced, which led to
performance issues that was worked around in this PR. By comparing
control points, we're able to get good performance without requiring the
workaround.
