Camera: Wait for the HEIC gainmap format callback

The HEIC gainmap muxer track cannot be added without
a valid format. Wait until the format message is received
before proceeding with further HEIC gainmap processing.

Flag: EXEMPT bugfix
Bug: 427246672
Test: atest -c -d cts/tests/camera/src/android/hardware/camera2/cts/ImageReaderTest.java#testHeicUltraHdr

Change-Id: Ie2dbc994e2c68c8eb7fbbc31d33bf001215d18db