Blender Git Loki

Transform: Optimize edge slide

The current edge slide is executed in this sequence:
- traverses all edges to find the ones selected,
- traverses each vertex of the selected edges,
- traverses each linked edge of the vertex to finally execute the code.

However the list of vertices that are part of selected edges are already
stored in `EdgeSlideData` through the `TransDataEdgeSlideVert *sv;` member.

Therefore, the code can be simplified as follows:
- traverses all `sv` in `EdgeSlideData`,
- get the `sv->v` vertex to finally execute the code.

Differential Revision: https://developer.blender.org/D5277