Export sparsity detection interface

[adrhill]

The interface for sparsity detection should be exported, or at least marked as public.
The exported symbols are very unlikely to cause name collisions:

• jacobian_sparsity
• hessian_sparsity
• AbstractSparsityDetector
• NoSparsityDetector

The same applies to the matrix coloring interface as well.

[ChrisRackauckas]

sounds fine to me.

[adrhill]

I'll open a PR if @gdalle doesn't object.

[gdalle]

Marked as public, definitely, but that would require bringing Compat as an additional dependency since the public keyword only lands in Julia 1.11.

Exports are essentially useless because they don't semantically denote public API, they just clutter the namespace. I would be okay with exporting the first two, but no one is ever gonna use the latter two in their code so I'm firmly against exporting those.

[gdalle]

On second thought it's not a great idea to export jacobian_sparsity and hessian_sparsity because Symbolics also defines functions with the same name (which are not just methods for the ADTypes functions). In other words, if Symbolics ever decides to export them, the code of anyone who wrote

using ADTypes, Symbolics

will be broken

[ChrisRackauckas]

Symbolics should extend.

[gdalle]

Unclear because the Symbolics functions apply to different data types (symbolic variables and expressions)