Migrate image diff from legacy diff to lit diff

This turned out much easier than expcted. The parent's responsibilty is
simply to provide the two LOST/FILE rows and implemeting the lookup
methods. We can just swap out the legacy builder for the new builder.

Of course, the entire builder hierarchy is still terrible and needs
further cleanup, but the first goal is to remove the remaining two deps
on the legacy diff builder. Once that is done we can start with the
actual cleanup.

Release-Notes: skip
Google-Bug-Id: b/280018642
Change-Id: Ic8f2f36a2e5086dd11c281eee210b39c5adc6533
(cherry picked from commit fe4a3872a1909f0dc288f59fa84ba54629566c06)
diff --git a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-builder-image.ts b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-builder-image.ts
index 0ea904a..f0cc69f 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-builder-image.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-builder/gr-diff-builder-image.ts
@@ -3,7 +3,6 @@
  * Copyright 2016 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {GrDiffBuilderSideBySide} from './gr-diff-builder-side-by-side';
 import {ImageInfo} from '../../../types/common';
 import {DiffInfo, DiffPreferencesInfo} from '../../../types/diff';
 import {RenderPreferences, Side} from '../../../api/diff';
@@ -11,13 +10,14 @@
 import {ImageDiffBuilder} from './gr-diff-builder';
 import {html, LitElement, nothing} from 'lit';
 import {customElement, property, query, state} from 'lit/decorators.js';
+import {GrDiffBuilderLit} from './gr-diff-builder-lit';
 
 // MIME types for images we allow showing. Do not include SVG, it can contain
 // arbitrary JavaScript.
 const IMAGE_MIME_PATTERN = /^image\/(bmp|gif|x-icon|jpeg|jpg|png|tiff|webp)$/;
 
 export class GrDiffBuilderImage
-  extends GrDiffBuilderSideBySide
+  extends GrDiffBuilderLit
   implements ImageDiffBuilder
 {
   constructor(