Delete entire juice stream when only one vertex remains after deleting another vertex

[bdach]

Closes #31425.

Matches handling of sliders:

osu/osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/SliderSelectionBlueprint.cs

Lines 478 to 483 in e7070bd

	// If there are 0 or 1 remaining control points, or the slider has an invalid length, it is in a degenerate form and should be deleted
	if (controlPoints.Count <= 1 || !HitObject.Path.HasValidLength)
	{
	placementHandler?.Delete(HitObject);
	return;
	}

[bdach]

Reason for having this virtual and the actual logic only live in the selection subclass is that the logic breaks placement if put here. There are other protections in place already against placement allowing zero length:

osu/osu.Game.Rulesets.Catch/Edit/Blueprints/JuiceStreamPlacementBlueprint.cs

Line 28 in e7070bd

protected override bool IsValidForPlacement => Precision.DefinitelyBigger(HitObject.Duration, 0);