With the goal of clearly differentiating between arrays and single elements, improving consistency across Blender, and using wording that's easier to read and say, change variable names for Mesh edges and polygons/faces. Common renames are the following, with some extra prefixes, etc. - `mpoly` -> `polys` - `mpoly`/`mp`/`p` -> `poly` - `medge` -> `edges` - `med`/`ed`/`e` -> `edge` `MLoop` variables aren't affected because they will be replaced when they're split up into to arrays in #104424.