## C++ tests copied from libavif.

### Copied as is

* avifalphanoispetest.cc
* avifanimationtest.cc
* avifdecodetest.cc
* avifprogressivetest.cc
* avifclaptest.cc

### Copied with changes

* avifmetadatatest.cc
  * Remove encoder tests and add more checks to the decoder test.
* avifgainmaptest.cc
  * Remove encoder tests.