[EMSUSD-3929] primvars:normals authored as float3[] instead of normal3f[]

**Describe the bug**
When Exporting via USD Exporter the normals are authored in a `float3` type.

**Steps to reproduce**
Steps to reproduce the behavior:
1. Create an object
2. Export Selected to a .usd file type
3. Be sure geometry normals are authored to primvars
4. Evaluate .usd in usd view

**Expected behavior**
Please refer to this documentation,
https://openusd.org/dev/api/_usd__page__datatypes.html#Usd_Roles

and this:
https://openusd.org/dev/api/class_usd_geom_point_based.html#ac9a057e1f221d9a20b99887f35f84480

This is spelled out in the USD schema itself: UsdGeomPointBased declares the attribute as `normal3f[] normals`, and the same type is expected for `primvars:normals`. Pixar's Sdf datatypes doc lists normal3f with role "Normal" / meaning "transform as a normal," while float3 has no role at all.

Repro: export any mesh with normals and inspect the .usda. You'll see `float3[] primvars:normals` where it should read `normal3f[]`.

**Fix**: author the attribute with SdfValueTypeNames->Normal3fArray instead of Float3Array. The values don't need to change, just the declared type.

Locate the USD Exporter code that authors primvars:normals; first reproduce the issue by exporting a mesh and inspecting the resulting .usda file. Confirm completion when the exported attribute is declared normal3f[] rather than float3[] while its values remain unchanged.

Written by the indexing model from the issue text.