vips: update to 8.18.3, fix gif dependency with new cgif-0.5.3 package

[yoshiyoshyosh]

Testing the changes

• I tested the changes in this PR: YES
  • libvips still works on everything I used it before, and now it can properly convert gifs

New package

• This new package conforms to the package requirements: YES
  • cgif is the "native" dependency of libvips for gif images. without it, gifs are encoded through its imagemagick module.

Local build testing

• I built this PR locally for my native architecture, x86_64-glibc

This PR supersedes #59216 (the author didn't fix requested changes, and I need to update vips now anyway...) and closes #59205

libvips does not use giflib for encoding gifs; it uses cgif. previously, gif encoding would fail and the giflib dependency was useless. (I should've realized something was up when inheriting the package, but I just never used vips for gif encoding myself. My bad!)