Bound sizes for tx3g atom parsing per track

Detect when media contains too much tx3g data, defined as max atom size
even if spread across multiple tx3g atoms. Also validate that any tx3g
atom has non-zero size.

When assembling the possibly many atoms, use a more efficient append/grow in a
local buffer and only attach it to the track meta data when the track is
complete; saves a possible O(n*n) copy/re-copy/re-copy behavior.

Bug: 124330204
Test: poc
Change-Id: I55ab88a4b650e508c0d49f9bd07284d9ddcf6361