Improve names of IRenderDimensions interface members

[Tyriar]

Fixes #3925

Before:

export interface IRenderDimensions {
  scaledCharWidth: number;
  scaledCharHeight: number;
  scaledCellWidth: number;
  scaledCellHeight: number;
  scaledCharLeft: number;
  scaledCharTop: number;
  scaledCanvasWidth: number;
  scaledCanvasHeight: number;
  canvasWidth: number;
  canvasHeight: number;
  actualCellWidth: number;
  actualCellHeight: number;
}

After:

export interface IRenderDimensions {
  css: {
    canvas: IDimensions; // previously: canvas*
    cell: IDimensions; // previously: actualCell*
  };
  device: { // previously: scaled*
    canvas: IDimensions;
    cell: IDimensions;
    char: IDimensions & IOffset;
  };
}