Navigation: Add descriptions to NavModelItems (#55669)

* add some descriptions!

* Update some descriptions

* Tweak playlist description

* fix unit tests + betterer

public/app/core/components/AppChrome/NavLandingPage.test.tsx

@@ -27,7 +27,7 @@ describe('NavLandingPage', () => {
   const mockChild3 = {
     text: 'Child 3',
     id: 'child3',
-    subTitle: 'Child 3 subtitle',
+    description: 'Child 3 subtitle',
     url: 'mock-section-url/child3',
     hideFromTabs: true,
     children: [
@@ -86,9 +86,9 @@ describe('NavLandingPage', () => {
     expect(screen.getByRole('heading', { name: mockChild3.text })).toBeInTheDocument();
   });
 
-  it('renders the subTitle for a nested section', () => {
+  it('renders the description for a nested section', () => {
     setup();
-    expect(screen.getByText(mockChild3.subTitle)).toBeInTheDocument();
+    expect(screen.getByText(mockChild3.description)).toBeInTheDocument();
   });
 
   it('renders a link for a nested child', () => {

public/app/core/components/AppChrome/NavLandingPage.tsx

@@ -40,7 +40,7 @@ export function NavLandingPage({ navId }: Props) {
               <div style={{ display: 'flex', alignItems: 'center' }}>
                 <h2 className={styles.nestedTitle}>{child.text}</h2>
               </div>
-              <div className={styles.nestedDescription}>{child.subTitle}</div>
+              <div className={styles.nestedDescription}>{child.description}</div>
               <div className={styles.grid}>
                 {child.children?.map((child) => (
                   <NavLandingPageCard

public/app/core/components/PageNew/PageHeader.tsx

@@ -11,7 +11,7 @@ export interface Props {
 
 export function PageHeader({ navItem, subTitle }: Props) {
   const styles = useStyles2(getStyles);
-  const sub = subTitle ?? navItem.subTitle;
+  const sub = subTitle ?? navItem.description;
 
   return (
     <>