feat(image): add 'default-image' ::part (carbon-design-system#10450)

### Related Ticket(s)

Closes carbon-design-system#10380

### Description

Adds `part` property with value of `image` to the rendered `<img>` tag.

### Testing Instructions

In the styles tab of the devtools, add a new style targeting `dds-image::part(image)`, and note that style added here impact the shadow root's `<img>` tag.

Would be good to have @dratzenboeck-ibm provide an SVG file with `#svgView` parameter to test with.

### Changelog

**New**

- dds-image::part(image)

packages/web-components/src/components/image/image.scss

@@ -1,5 +1,5 @@
 //
-// Copyright IBM Corp. 2020, 2022
+// Copyright IBM Corp. 2020, 2023
 //
 // This source code is licensed under the Apache-2.0 license found in the
 // LICENSE file in the root directory of this source tree.

packages/web-components/src/components/image/image.ts

@@ -188,6 +188,7 @@ class DDSImage extends StableSelectorMixin(
           src="${defaultSrc}"
           alt="${alt}"
           aria-describedby="image-caption long-description"
+          part="image"
           loading="lazy" />
       </picture>
       <div id="long-description" class="${prefix}--image__longdescription">

packages/web-components/tests/snapshots/dds-image.md

@@ -13,6 +13,7 @@
     aria-describedby="image-caption long-description"
     class="bx--image__img"
     loading="lazy"
+    part="image"
     src=""
   >
 </picture>
@@ -39,6 +40,7 @@
     aria-describedby="image-caption long-description"
     class="bx--image__img"
     loading="lazy"
+    part="image"
     src=""
   >
 </picture>