Merge ICharAtlasRequest with ICharAtlasConfig

ICharAtlasRequest and ICharAtlasConfig need almost exactly the same set
of information, so it's simpler if we just merge the two types.

As an added bonus, this also adds devicePixelRatio to the config, which
helps guarantee that we won't ever accidentally end up with an atlas
using a different pixel ratio than we need.

src/renderer/Types.ts

@@ -5,6 +5,7 @@
 
 import { ITerminal } from '../Types';
 import { IEventEmitter, ITheme } from 'xterm';
+import { IColorSet } from '../shared/Types';
 
 /**
  * Flags used to render terminal text properly.
@@ -39,14 +40,8 @@ export interface IColorManager {
   colors: IColorSet;
 }
 
-export interface IColorSet {
-  foreground: string;
-  background: string;
-  cursor: string;
-  cursorAccent: string;
-  selection: string;
-  ansi: string[];
-}
+// TODO: We should probably rewrite the imports for IColorSet, but there's a lot of them
+export { IColorSet };
 
 export interface IRenderDimensions {
   scaledCharWidth: number;