Interpolate UV coordinate of DensePose CSE

## 🚀 Feature
Currently the DensePoseOutputsTextureVisualizer class only output UV coordinates of closest vertex, thus cannot generate a complete texture map from it. The visualizer should output UV coordinates with interpolation so each pixel map to a unique uv coordinate.

## Motivation & Examples
the mapped UV coordinates of vertex:

Start by locating the DensePoseOutputsTextureVisualizer implementation and reviewing how it currently selects the closest vertex UV coordinate. Determine how interpolated UV coordinates should be produced for each pixel, then verify that the visualizer can generate a complete texture map with unique per-pixel UV coordinates.

Written by the indexing model from the issue text.