MediaCodec: Make copy of format msg when callback output format changed.

When notifying the client of output format changed through async
callbacks, the format message is directly referencing its internal
object. It is not thread-safe for the format message.

Make copy of the format message before async callback to both NDK
and NuPlayer::Decoder client. Not just for the ndk client.

Bug: 412946306
Test: MediaPlayerTest
Flag: EXEMPT bugfix
Signed-off-by: Fang Zhaohui <fangzhaohui@xiaomi.corp-partner.google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:a996ab6b0085e45530321dd5af8675dcdba0aa9c)
Merged-In: I6cc02ed8b1d76cdc30ff6d5b608feaedbd9ababe
Change-Id: I6cc02ed8b1d76cdc30ff6d5b608feaedbd9ababe