Add n-dimensional PowerCone

@lkapelevich and @HFriberg have been emailing me about the upcoming CBF v4, https://cblib.zib.de/doc/format4.pdf, which proposes to add an n-dimensional PowerCone.

We've talked about this somewhat before: https://github.com/jump-dev/MathOptInterface.jl/issues/977

There are two proposed variants (plus their dual cones).

I have no strong feelings on which ones (if any) we should adopt. But I'd like to somewhat reign in having a litany of very similar cones.

Radial

Hypograph

Clarabel

Clarabel has native support for the radial with the restriction that $\sigma=1$ https://clarabel.org/stable/api_cone_types/

Hypatia

Hypatia has both https://jump.dev/Hypatia.jl/stable/api/cones/#Hypatia.Cones.GeneralizedPower and https://jump.dev/Hypatia.jl/stable/api/cones/#Hypatia.Cones.HypoPowerMean

Mosek

Mosek has support for radial: https://docs.mosek.com/latest/capi/alphabetic-functionalities.html#mosek.task.appendprimalpowerconedomain

先阅读 issue #977 以及其中链接的 CBF v4、Clarabel、Hypatia 和 Mosek cone 定义。由于没有指定 repository 文件或 tests，因此首先确定现有的 cone 接口，并决定哪一种 radial 或 hypograph 变体（包括 dual）是合适的。完成的标准是：选定的 n-dimensional PowerCone 设计已按照项目现有的 cone API 一致地实现，并通过其 tests 验证。