Update EmojiCompat sample

* Initialize EmojiCompat during activity.onCreate instead of
  application.onCreate.
* Add information about downloading the font during install time.
* Update tools version and target SDK.

Test: N/A
Bug: 74244504
Bug: 75983734
Change-Id: I1dc367a2abefd66fa63ed953acafc71832fd1f5d
(cherry picked from commit 6fc687c87842ee22db330c123fe08ed7bcfcb262)