Revert "[rust png] Extract `SkPngEncoderBase::onEncodeRows`."

This reverts commit a56089f7e31447e9e1a81206927e7c19a61c60bd.

Reason for revert: Breaking G3

Original change's description:
> [rust png] Extract `SkPngEncoderBase::onEncodeRows`.
>
> This CL extracts some `src/encode/SkPngEncoderImpl.cpp` code and moves
> it into a reusable `src/encode/SkPngEncoderBase.h/.cpp` (continuing the
> effort from http://review.skia.org/922676).  In particular,
> `SkPngEncoderImpl::onEncodeRows` has been moved into
> `SkPngEncoderBase::onEncodeRows` and the `libpng`-specific parts have
> been abstracted away into `onEncodeRow` and `onFinishEncode` virtual
> methods.  The motivation is the desire to reuse this code from
> `SkPngRustEncoderImpl` in a future CL.
>
> Bug: chromium:379312510
> Change-Id: Ic26f4516bcba4ad8e8a9773cea4e9a05eb761160
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/923336
> Reviewed-by: Florin Malita <fmalita@google.com>
> Commit-Queue: Ɓukasz Anforowicz <lukasza@google.com>

Bug: chromium:379312510
Change-Id: I22ac7563e153b0cf5c88949bd554775573b3dbd4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/927098
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
4 files changed