[hdrnet] Add notebook to fit a single bilateral grid to a source, target pair
[hdrnet] Add notebook to fit a single bilateral grid to a source, target pair

* Add hdrnet jax and optax as a dependency of the gcam colab
* Change bilateral slice test to use tf2 directly (we don't really need to force use tf1 anywhere but the HDRnet training code)
* Fix bilateral_slice jax gradient computation for jax.jit

PiperOrigin-RevId: 445521193

google/hdrnet,google/hdrnet,google/hdrnet