heif: add muxer support for adding still images

This change adds basic support for adding still images to a
heif container.

bug: 63633199

test:
Locally built test app that adds more than one still images
and video sequences to a heif container. Verified the muxed
file can be played by locally built heif viewer app that
uses MediaExtractor/MediaMetadataRetriever/MediaPlayer apis.

Tested media post-submit CTS on Pixel2XL.

Change-Id: I185bbbbed3dbb4e76d64bcf7323ee44a42cc8623
diff --git a/media/extractors/mp4/ItemTable.cpp b/media/extractors/mp4/ItemTable.cpp
index 9a6cb64..85c66b2 100644
--- a/media/extractors/mp4/ItemTable.cpp
+++ b/media/extractors/mp4/ItemTable.cpp
@@ -1425,7 +1425,7 @@
     meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_IMAGE_ANDROID_HEIC);
 
     if (image->itemId == mPrimaryItemId) {
-        meta->setInt32(kKeyIsPrimaryImage, 1);
+        meta->setInt32(kKeyTrackIsDefault, 1);
     }
 
     ALOGV("image[%u]: size %dx%d", imageIndex, image->width, image->height);