Registry of `add_any` and `pad`

[zgbkdlm]

Hi,

I have encountered the following warnings of unregistered functions. These functions add_any and pad seem to be JAX primitives and I don't find any intructions in README.md for how to register them. Do you have any example?

WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/jvp.py:493:15 (get_jvp_function.<locals>.merged_fwd)) - add_any not in registry. The following call might be slow as we will compute the full hessian.
WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/jvp.py:493:15 (get_jvp_function.<locals>.merged_fwd)) - add_any not in registry. The following call might be slow as we will compute the full hessian.
WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/utils.py:98:12 (flat_wrap.<locals>.new_fn)) - pad not in registry. The following call might be slow as we will compute the full hessian.
WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/utils.py:98:12 (flat_wrap.<locals>.new_fn)) - pad not in registry. The following call might be slow as we will compute the full hessian.
WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/ad.py:70:39 (jacrev.<locals>.jacfun.<locals>.flat_f)) - pad not in registry. The following call might be slow as we will compute the full hessian.
WARNING:[folx](/home/.venv/lib/python3.12/site-packages/folx/ad.py:70:39 (jacrev.<locals>.jacfun.<locals>.flat_f)) - pad not in registry. The following call might be slow as we will compute the full hessian.

[n-gao]

Thanks a lot for your interest in folx! :)

To register a function for your own code, you can simply add

import jax
from folx import register_function, wrap_forward_laplacian

register_function(jax._src.ad_utils.add_any_p,wrap_forward_laplacian(
        jax.lax.add, flags=FunctionFlags.LINEAR, in_axes=()
    )
)

For a PR, please add it to the _LAPLACE_FN_REGISTRY dictionary in wrapped_functions.py.

For the pad primitive, it's a bit more complicated since the results depend on the padding mode. It depends on whether value is a FwdLaplArray. If that's the case, the logic needs special handling. For non-FwdLaplArray pad values, one can simply rely on the FunctionFlags.INDEXING default.

Please feel free to open a PR to fix this issue.