Reland: Add ISO 21496-1 gainmap parsing

To SkGainmapInfo, add the functions ParseVersion, Parse,
SerializeVersion, and serialize. These generate the ISO 21496-1
binary blobs.

Reverted because of unused function in test. Moved function inside
appropriate ifdef.

Bug: b/338342146
Change-Id: I98436f3757f08668c3129b02f40dd5bbe223a073
Reviewed-by: Brian Osman <>
Reviewed-by: Christopher Cameron <>
Commit-Queue: Christopher Cameron <>
6 files changed