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/TextWidget.ts

@@ -26,7 +26,7 @@ export class TextWidget extends BaseWidget implements IStringWidget {
     y,
     width,
     show_text = true,
-    margin = 15,
+    margin = BaseWidget.margin,
   }: DrawWidgetOptions) {
     // Store original context attributes
     const originalTextAlign = ctx.textAlign