Merge MaterialX:main 1.38.5 to adsk_contrib

[ashwinbhat]

Please see main changelog for details. One of the main changes is how libraries are handled that impacts MaterialXRuntime, OGSFX, OGSXML and Arnold Shader Generators. Key changes to Autodesk fork:

• OGSFX/OGSXML tests have been updated
• disabled MaterialXRuntime tests.
• disabled adsk_shader tests since they use textures from libraries which is not recommended. Needs further discussion.
• The Arnold tests pass but they emit the following warnings. Needs further investigation.

  
  77: --- Wrote temp arnold mtlx file to: F:\source\MaterialX-adsk-fork-dev\_build_test\bin\resources\Materials\TestSuite\stdlib\version\multiple_version_test.v2_implicit_out_arnold.xml
  77: Render: Arnold TestSuite completed in 133.292s
  77: ===============================================================================
  77: All tests passed (1697 assertions in 1 test case)
  77:
  77/77 Test #77: MaterialXTest_Render_Arnold_TestSuite ........................   Passed  133.43 sec