Revert "Refactor SkJpegXmp into SkXmp which is more generic."

This reverts commit 311c667507c022cb92aa8a6354bc90ec48ee6593.

Reason for revert: breakage on tree

Original change's description:
> Refactor SkJpegXmp into SkXmp which is more generic.
>
> Useful for formats other than jpeg that would use the same
> gainmap xmp format for example.
>
> Change-Id: Id1e69032a4566e96fdc4d0038ee6a6b39ea7ed95
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/699656
> Reviewed-by: Christopher Cameron <ccameron@google.com>
> Commit-Queue: Christopher Cameron <ccameron@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Change-Id: Ifde521be67f9f7e6555478746232d57f8fa24af1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/710376
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
16 files changed