Cleanup: Removing monkeypatches for litegraph logic (#5902)

## Summary

Putting the litegraph specific pieces into litegraph itself, using the
CanvasGraph and LiteGraphGlobal to coordinate options.

This was one part of the Image Previews reloading/calculating with every
canvas draw.

## Review Focus

Is this keeping things decoupled enough?
Is this the right place to put things?
Are there assumptions about the options that I'm missing here?

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5902-WIP-Removing-monkeypatches-for-litegraph-logic-2816d73d3650818b860ec73579b89b54)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

tests-ui/tests/litegraph/core/__snapshots__/litegraph.test.ts.snap

@@ -61,6 +61,7 @@ LiteGraphGlobal {
   "NODE_COLLAPSED_WIDTH": 80,
   "NODE_DEFAULT_BGCOLOR": "#353535",
   "NODE_DEFAULT_BOXCOLOR": "#666",
+  "NODE_DEFAULT_BYPASS_COLOR": "#FF00FF",
   "NODE_DEFAULT_COLOR": "#333",
   "NODE_DEFAULT_SHAPE": 2,
   "NODE_ERROR_COLOUR": "#E00",
@@ -79,6 +80,7 @@ LiteGraphGlobal {
     "#224",
     "#626",
   ],
+  "NODE_OPACITY": 0.9,
   "NODE_SELECTED_TITLE_COLOR": "#FFF",
   "NODE_SLOT_HEIGHT": 20,
   "NODE_SUBTEXT_SIZE": 12,
@@ -161,6 +163,8 @@ LiteGraphGlobal {
   "macTrackpadGestures": false,
   "middle_click_slot_add_default_node": false,
   "mouseWheelScroll": "panning",
+  "nodeLightness": undefined,
+  "nodeOpacity": 1,
   "node_box_coloured_by_mode": false,
   "node_box_coloured_when_on": false,
   "node_images_path": "",