Overhaul node computeSize - use actual text width (#962)

### Node resize overhaul

- Precisely calculates node minimum size
- Prevents input & output overlap
- Prevents (normal*) widgets from rendering text over the edge of nodes
- Performance impact was sub-millisecond for normal usage in a 500-node
graph


![image](https://github.com/user-attachments/assets/5b6a6cc7-a752-4d7e-bcdf-b4bc8df26c51)

_Minimum size for a few example node configurations_

### Widgets

- Converts hard-coded draw render values to class static properties
- Adds widget button draw function for left/right arrow widgets

_*_ Exception: `control_after_generate`, as it is not a true input /
widget. A check may be added later to handle this special case.

src/widgets/NumberWidget.ts

@@ -43,7 +43,7 @@ export class NumberWidget extends BaseWidget implements INumericWidget {
     y,
     width,
     show_text = true,
-    margin = 15,
+    margin = BaseWidget.margin,
   }: DrawWidgetOptions) {
     // Store original context attributes
     const originalTextAlign = ctx.textAlign
@@ -66,19 +66,7 @@ export class NumberWidget extends BaseWidget implements INumericWidget {
     if (show_text) {
       if (!this.computedDisabled) {
         ctx.stroke()
-        // Draw left arrow
-        ctx.fillStyle = this.text_color
-        ctx.beginPath()
-        ctx.moveTo(margin + 16, y + 5)
-        ctx.lineTo(margin + 6, y + height * 0.5)
-        ctx.lineTo(margin + 16, y + height - 5)
-        ctx.fill()
-        // Draw right arrow
-        ctx.beginPath()
-        ctx.moveTo(width - margin - 16, y + 5)
-        ctx.lineTo(width - margin - 6, y + height * 0.5)
-        ctx.lineTo(width - margin - 16, y + height - 5)
-        ctx.fill()
+        this.drawArrowButtons(ctx, margin, y, width)
       }
 
       // Draw label