USD Render: prefix the AOV with the render product name

[MustafaJafar]

Changelog Description

prefix the AOV with the render product name.
Hopefully, resolve #105

Note

This PR was made to show the issue where different render products can export the same render var(AOV) but with different configurations, such as Beauty and Deep Beauty.
In this essence, the publisher is not creating enough instances for them and just keep showing this error message:

Multiple render products are identified as the same AOV 
which means one of the two will not be ingested during 
publishing. AOV: '%s'", aov_identifier

Important

For this PR to be merged, we need to ensure it's backwards compatible
where the layers shouldn't get a new name or being too long and cluttered.

Additional Info

Here's an example scene. Please let me now if it's not a good example scene.
Expr_USD_Render_Houdini_v001.zip

Demo

Here are some screenshots.

When Dcm has one AOV

When Dcm has multiple AOVs

Testing notes:

1. Add multiple render vars and multiple products.
2. Feel free to us the same render var within different render products.
3. Publish USD render.

[moonyuet]

Looks good.

[MustafaJafar]

Closing this PR in favor of #120