[RFC]: add `blas/ext/base/gsort`

Similar to `blas/ext/base/gsum`, `stats/strided/gmean`, etc, this package is intended to provide an "opaque" sort API in which the underlying algorithm is not fixed, but is allowed to change in the future.

For now, `gsort` should simply wrap `gsorthp` (heapsort). In the future, we can swap with an alternative algorithm. Having this package will allow us to have a "general" `blas/ext/sort` API.