Add 3-point circle tool (#4832)

* Add 3-point circle tool

This adds a 1st pass for the 3-point circle tool.

There is disabled code to drag around the 3 points and redraw the circle and
a triangle created by those points. It will be enabled in a follow-up PR
when we have circle3Point in the stdlib.

For now, all it does is after the 3rd click, will insert circle center-radius
KCL code for users to modify.

* PR comments

src/clientSideScene/sceneInfra.ts

@@ -62,6 +62,8 @@ export const ARROWHEAD = 'arrowhead'
 export const SEGMENT_LENGTH_LABEL = 'segment-length-label'
 export const SEGMENT_LENGTH_LABEL_TEXT = 'segment-length-label-text'
 export const SEGMENT_LENGTH_LABEL_OFFSET_PX = 30
+export const CIRCLE_3_POINT_DRAFT_POINT = 'circle-3-point-draft-point'
+export const CIRCLE_3_POINT_DRAFT_CIRCLE = 'circle-3-point-draft-circle'
 
 export interface OnMouseEnterLeaveArgs {
   selected: Object3D<Object3DEventMap>