Bifrost graphs are not property exported to Arnold USD files

**Describe the bug**
Bifrost graphs can live in `.ass` files just fine, but inside an Arnold-USD they do not execute. This is probably due to the input0 serialized data which is not converted in the same way in the two plugins.

**To Reproduce**
Steps to reproduce the behavior:
1. In Maya, create a Bifrost graph which creates a sphere using create_mesh_sphere.
2. Export a `.ass` file with expand procedurals OFF
3. Export an Arnold USDA file with expand procedurals OFF
4. Kick the .ass file file (see: https://docs.arnoldrenderer.com/display/A5AFMUG/Bifrost+Graph). It will render correctly.
5. Kick the .usd file. It will not render correctly and give an error message.

```
00:00:05 579MB ERROR | [bifrost] /bifrostGraph1/bifrostGraphShape1: input input0 is missing the bifrost:input0 declared parameter
00:00:05 580MB ERROR | [proc] /bifrostGraph1/bifrostGraphShape1: error in user init from
```

Inside the files, you can see the input0 serialized data is rendered differently in .ass and usda forms.

See also: BIFROST-7914

**Used Software Versions**
- Arnold: 7.1.3
- MayaUSD 0.18
- OS: Windows 10

[sphere_ass_and_usd.zip](https://github.com/Autodesk/arnold-usd/files/9984436/sphere_ass_and_usd.zip)