Revert "add runtime registration for encoders"

This reverts commit 940c3f136dcbfd63b250087a688dd0a802e3f9fe.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> add runtime registration for encoders
> 
> If we want to make these external dependencies mix-and-match in Google3,
> we'll need to group together the encoders and decoders, everything that
> dependends on each external library.
> 
> I was tempted to try to remove these generic encoder entrypoints and
> replace them with calls to the direct equivalents, but I'm not sure
> that's necessary.  I think we can just register encoders like decoders.
> 
> Change-Id: I41d2d1bb3ceb1daafa62c95d345eb6a70249be75
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213880
> Commit-Queue: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

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

Change-Id: I3ee9353ca6b3c6c11feba0503b672d8986a347be
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/214107
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
6 files changed