API: Add sparse Acessor
* Adds a Series.sparse accessor
* Adds several methods to SparseArray to for use via the accessor

Closes #23148.

This should provide all the methods / attributes that were available on SparseSeries, but not Series.

Right now the docs for `.sparse.from_coo` and `to_coo` seem to be broken. It's a bit strange since they're implemented on the accessor (they don't make sense on the Array)