cogl: FP16 fixes, tests, and various cleanups
This adds
- fp16 offscreen tests
- fp16 packing/unpacking
- fixes readPixels functionality
- fixes packing 8bpc opaque pixel formats
- fixes advertising float rgba1010102 formats
cogl/bitmap-conversion: Support packing fp16 formats
could use some feedback because packing/unpacking via floats is kind of weird. The C type float
is also not guaranteed to be 32 bits, if a float doesn't fit in an integer the result is undefined.
Includes !3429 (merged).