Colorset Names created with internal value

**Describe the bug**
. There are some object assets if their vertex colors were made with the Maya's Per Instance Unshared setting, the colorset names are created with an internal (0) , for example VCP_Color(0) and VCP_Alpha(0)
With mayaUSD plugin when exporting these vertex color data, it seems they take the whole string VCP_COLOR(0) directly as the attribute name but (0) is invalid character in USD and would fail during its own validation, so the USD export would fail.

For example, if I export an .ma file (example: lightWallMISCandle_01.ma) containing an asset with mayaUSD plugin then we get this error:

/ Error: Cannot create attribute spec on with invalid name 'primvars:VCP_Color(0)' -- and 7 similar

We have been trying to convert these kind of vertex color to a different mode (Per Instance Unshared mode might not be necessary), and test if that breaks anything. But this can be an issue with the plugin since the (0) data is created by Maya and not user, MayaUSD plugin might be able to doing something like converting the (0) to _0_  during export to handle attribute names like this. For example, DAE export converts parenthesis to underscore.

Just renaming the colorset doesn't change the (0) part, Maya adds it no matter what as long as it's created with the Per Instance Unshared mode

**Steps to reproduce**
Steps to reproduce the behavior:
Please reach out to msnider@ea.com for more information