[DO NOT MERGE] Wait for preloading images to complete before inflating notifications

 NotificationContentInflater waits on SysUiBg thread for images to load, with a timeout
 of 1000ms.

Test: 1. Build a test app that posts MessagingStyle notifications with a huge image (8k+) set as data Uri.
 2. SystemUi should not ANR
 3. adb logcat | grep NotificationInlineImageCache  - shows timeout/cancellation logs

Bug: 252766417
Bug: 223859644
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2a2da8935ab70163044c34d7b0d9b9ed4cb91a76)
Merged-In: I341db60223214cf2282b5c0270e343e1ce95fa01
Change-Id: I341db60223214cf2282b5c0270e343e1ce95fa01