ViewRootImpl: Ensure seqId only increases

We could process an earlier scheduled MSG_RESIZED after
a later executed relayoutWindow. In this case we might
accidentally move the seqId backwards, which could mess
up our logic. While we are touching this area, we
take the opportunity to ensure SyncHandlers execute
in the order they were added.

Bug: 161810301
Bug: 227561299
Test: Existing tests pass
Change-Id: I8e5ceea1ef34e4da94807582c89a33df95772c04