fix(material/dialog): dialog name on mac only using aria-label

Fixes bug with Angular Components Dialog component on Mac
whether using Chrome or Firefox the screenreader does not
read the dialog name/title unless it is using an aria-label.
Updates the dialog-content-directives to read/apply the aria-
labelledby and aria-describedby values if they exist.

Fixes b/274674581

Author: essjay05

src/material/dialog/dialog-content-directives.ts

@@ -34,6 +34,8 @@ let dialogElementUid = 0;
   host: {
     '(click)': '_onButtonClick($event)',
     '[attr.aria-label]': 'ariaLabel || null',
+    '[attr.aria-labelledby]': 'ariaLabelledBy || null',
+    '[attr.aria-describedby]': 'ariaDescribedBy || null',
     '[attr.type]': 'type',
   },
 })