Update Spinner (#9345)

### WHY are these changes introduced?

Resolves https://github.com/Shopify/polaris-summer-editions/issues/72


### WHAT is this pull request doing?

- Updates the Spinner `fill` color

### How to 🎩

Review on
[Storybook](https://5d559397bae39100201eedc1-pyvdrbupij.chromatic.com/?path=/story/all-components-spinner--all)
- Ensure beta flagged Spinner styles render as expected
- Ensure no regressions to the existing Spinner styles

Author: lgriffee

polaris-react/src/components/Spinner/Spinner.scss

@@ -1,3 +1,5 @@
+@import '../../styles/common';
+
 $small-size: 20px;
 $large-size: 44px;
 
@@ -10,6 +12,10 @@ $large-size: 44px;
   animation: var(--p-motion-keyframes-spin) var(--p-motion-duration-500) linear
     infinite;
   fill: var(--p-color-border-info);
+
+  #{$se23} & {
+    fill: var(--p-color-bg-interactive);
+  }
 }
 
 .sizeSmall svg {

polaris-react/src/components/Spinner/Spinner.stories.tsx

@@ -14,6 +14,16 @@ export default {
   component: Spinner,
 } as ComponentMeta<typeof Spinner>;
 
+export function All() {
+  return (
+    <>
+      <Default />
+      <Small />
+      <WithFocusManagement />
+    </>
+  );
+}
+
 export function Default() {
   return <Spinner accessibilityLabel="Spinner example" size="large" />;
 }