Add support for compressed texture formats in Qt 3D Studio

Qt 3D Studio needs to support compressed texture formats if those are available in the runtime environment, supported by the OpenGL driver and GPU, natively.

The compression formats we should try to load (in order of preference) are:
1. ETC2 (Khronos standard, average quality, supported in GLES 3 HW and many GLES 2 HW)
2. S3TC (old, not the best quality, but widely supported in older GPUs)
3. ASTC (modern, best quality for MB, supported by many modern GPUs)

Container formats we should support are:
1. KTX (Khronos standard)

We should NOT emulate support in SW on the runtime as that can lead to customers using suboptimal formats. On the editor this might be necessary to support these formats on desktop HW.