Problems when jitting Adafactor with inject_hyperparams.

When wrapping `optax.adafactor` with `optax.inject_hyperparams` without specifying `static_args`

```
optax.inject_hyperparams(optax.adafactor)(learning_rate=0.1)
```

the `init` function of the resulting `GradientTransformation` cannot be jit compiled. The reason is that by default `inject_hyperparams` treats all arguments as dynamic and one of the argument has to be static to avoid a `TracerError`. A workaround is to specify the static argument:

```
optax.inject_hyperparams(optax.adafactor, static_args=("min_dim_size_to_factor",))(learning_rate=0.1)
```

However, this is not ideal since it requires the user to know which arguments should be static and which ones can be dynamic.

We should:

- Add a test to check whether any other optimizers are affected.
- Change the implementations so that all optimizers wrapped in inject_hyperparams can be jit compiled without any arguments being specified as static.