[Feature] 整理 libcpu 下的 Kconfig 文件 | Separate Kconfig under libcpu to each architectures

[polarvid]

Describe problem solved by the proposed feature

当前 rt-thread/libcpu/Kconfig 文件内容较混乱。每个架构单独的配置完全可以拆解到独立的目录下维护。

Describe your preferred solution

No response

Describe possible alternatives

No response

[ComerLater]

有道理，我也支持