Add type alias support to the reverse bindings (#USDU-3 part 2)

[judubu]

Purpose of this PR

Ticket/Jira #:

USD allows certain attribute type to be given roles (aliases) to help unambiguously determine how data should be interpreted.
Ex:

• float2 can be given the texcoord2 when used for a uv primvar
• float3 can be given the point/normal/vector role ...

This is a problem when using our reverse bindings which let the USD type drive the C# type the primvar data should deserialized to. The reverse bindings are useful in the case a given attribute can be defined as multiple types. Typically UVs primvars can be defined as float2/float3/half2/half3/double2/double3 and as such can be also given the role of texcoord2f/texcoord3f/texcoord2h/texcoord3h/texcoord2d/texcoord3d .... As we already have a 1-to-1 mapping to Unity type for the standard types (float2, float3, ...) we can't augment the mapping to support roles.

This PR adds a way to define aliases for a given type and allow the reverse binding to convert roles to their canonic type before doing the type lookup.

Testing

Functional Testing status:

Performance Testing status:

Overall Product Risks

Complexity:

Halo Effect:

Additional information

Note to reviewers:

Reminder:

• Add entry in CHANGELOG.md (if applicable)

[jcowles]

This is awesome!

I do think we should keep the data private (typeAliases) and wrap it with a public API, but other than that, it looks great.

[clusty]

Aggree with @jcowles 's comments

[jcowles]

Ship it!