Do not restrict design image width in any case

Previously we were, by default, restricting image height/width to 100%.
This meant that long-and-slim images would be very
hard to see, and the user could not zoom in
to inspect closely.

This commit removes this CSS restriction, meaning that images
will default to `min(100% width, natural width)`

ee/app/assets/javascripts/design_management/components/image.vue

@@ -83,7 +83,7 @@ export default {
 </script>
 
 <template>
-  <div class="m-auto js-design-image" :class="{ 'h-100 w-100 d-flex-center': !imageStyle }">
+  <div class="m-auto js-design-image">
     <img
       ref="contentImg"
       class="mh-100"

ee/changelogs/unreleased/full-width-default-design-view.yml

+---
+title: Default design images to 100% of viewport width
+merge_request: 25327
+author:
+type: added

ee/spec/frontend/design_management/components/__snapshots__/image_spec.js.snap

@@ -2,7 +2,7 @@
 
 exports[`Design management large image component renders image 1`] = `
 <div
-  class="m-auto js-design-image h-100 w-100 d-flex-center"
+  class="m-auto js-design-image"
 >
   <img
     alt="test"
@@ -14,7 +14,7 @@ exports[`Design management large image component renders image 1`] = `
 
 exports[`Design management large image component renders loading state 1`] = `
 <div
-  class="m-auto js-design-image h-100 w-100 d-flex-center"
+  class="m-auto js-design-image"
   isloading="true"
 >
   <img