Fix token handling in functional nodegraphs

[kwokcb]

Issue

Tokens on nodedefs are not checked when resolving inputs on nodes in a functional nodegraph.
Update: #2361

Change

Patch token search to check nodedef tokens when applying token resolution

Test

Modified existing token test and added in nodedef case.
Example below is evaluation of an instance of a definition using tokens to resolve the input file name to an unlit shader. The token is the image name.

<nodedef name="ND_token" node="token_image" >
    <token name="Image_Name" type="string" value="grid" uiname="Image Name" />
    <token name="Image_Extension" type="string" value="png" uiname="Image Extension" />
    <output name="out" type="color3"></output>
  </nodedef>
  <nodegraph name="NG_token" nodedef="ND_token">
    <tiledimage name="tiledimage" type="color3" nodedef="ND_tiledimage_color3">
      <input name="file" type="filename" uniform="true" value="resources/Images/[Image_Name].[Image_Extension]" />
    </tiledimage>
    <output name="out" type="color3" nodename="tiledimage" />
  </nodegraph>
  <nodegraph name="token_nodedef_graph">
    <token_image name="token_image1" type="color3">
    </token_image>
    <output name="out" type="color3" nodename="token_image1"></output>
  </nodegraph>

[jstone-lucasfilm]

This looks like a good change to me, thanks @kwokcb!