Revert "manually register codecs in DM"

This reverts commit 9b2633e294de873d7c00201f26b033e0296747e9.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> manually register codecs in DM
> 
> We'll want to do this when we've got Google3 refactored
> to slice out each of these four codecs into its own little target.
> 
> Small tweaks to make SkPngCodec match the pattern of the rest.
> 
> Should be harmless to have both the compile-time and runtime
> registration, right?
> 
> Change-Id: Ic72394764ac267758dc1023e85f3d0c4b655d420
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213872
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,scroggo@google.com,brianosman@google.com

Change-Id: If3272ef1985757a93ada229f833408d4bf83ddfb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/214108
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed