Fix slow performance of polygon generation tool

[minetoblend]

Reusing the hitobjects now instead of removing them and regenerating everything from scratch each time. Also fixes the flashing whenever the polygon updates.

I put tryCreatePolygon() behind Scheduler.AddOnce for good measure, not sure if this is actually required as it's plenty fast either way now.

Before:

https://github.com/user-attachments/assets/fc2916ca-c742-4c84-be91-d46430c596bd

After:

https://github.com/user-attachments/assets/9cb73445-a3bb-4d54-a089-37e56c1ead08

[bdach]

How much of the "performance gain" here is the "reuse of objects"? I'd wager the .AddOnce() is doing the heavy lifting here if anything.

[minetoblend]

The majority of it comes from reusing the objects.

For comparison: (All the videos are recorded on release builds btw)

Index: osu.Game.Rulesets.Osu/Edit/PolygonGenerationPopover.cs
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/osu.Game.Rulesets.Osu/Edit/PolygonGenerationPopover.cs b/osu.Game.Rulesets.Osu/Edit/PolygonGenerationPopover.cs
--- a/osu.Game.Rulesets.Osu/Edit/PolygonGenerationPopover.cs	(revision 7e439be9eca9e626a080defc0cd24da933072710)
+++ b/osu.Game.Rulesets.Osu/Edit/PolygonGenerationPopover.cs	(date 1728640773096)
@@ -125,7 +125,7 @@
             tryCreatePolygon();
         }
 
-        private void scheduleRefresh() => Scheduler.AddOnce(tryCreatePolygon);
+        private void scheduleRefresh() => tryCreatePolygon();
 
         private void tryCreatePolygon()
         {

https://github.com/user-attachments/assets/467e06fa-bec3-4c68-8ad5-003b9c99f539

[minetoblend]

Ran it one more time with just Scheduler.AddOnce to double check, and it looks like it actually does have a noticeable effect, albeit much less than with just reusing the objects.

https://github.com/user-attachments/assets/fd417118-f96c-4f48-9edf-d4fd021d5da6