fuzzing: Add a fuzzer that has some valid resources and uses these
When fuzzing we want to avoid and early reject because a resource doesn't exist or because the command buffer size is not correct. Therefore, this fuzzer creates a number of buffers and textures, and when working a fuzzer blob, the blob is split into commands and the sizes of the commands are adjusted according to the sizes that are expected for each command, and the resource handles are replaced by handles of the previously created resources.
The first few patches are for fixes:
Then the series contains fixes to the test infrastructure to make it possible the re-use it for fuzzing, and a few more error messages are added on the decoding side.