Fix #53580: During resize gdImageCopyResampled cause colors change

We port the upstream fix[1], and also revert commit a3383ac3d7[2] which
is now obsolete, and also not part of libgd. E

Fix #53580: During resize gdImageCopyResampled cause colors change

We port the upstream fix[1], and also revert commit a3383ac3d7[2] which
is now obsolete, and also not part of libgd. Especially the change to
gd.png.c was at best a half-baked optimization.

[1] <https://github.com/libgd/libgd/commit/a24e96f01989bf9ca05a08d33862a08d6f4c4ed6>
[2] <https://github.com/php/php-src/commit/a3383ac3d7e21e54b1d7d89f308088d0692abc9f>

Closes GH-7402.

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