support StaticArrays

It would be nice if the various `rand(...)` functions supported returning an `SMatrix`, for example if `::Val{n}` is passed instead of `n::Integer`.

This improves performance and reduces memory allocations in cases where lots of small matrices need to be sampled. e.g. see [this example from discourse](https://discourse.julialang.org/t/code-speed-decreases-when-loop-number-increases/78920) which generates lots of 2x2 and 4x4 Haar-distributed unitary matrices.

首先定位 RandomMatrices.jl 中的各种 rand(...) 函数，并检查它们目前如何接受整数维度。检查 SMatrix 参数和 Val{n} 参数如何适配现有 API，然后验证是否可以在不产生所述内存分配和性能成本的情况下返回小型 Haar 分布酉矩阵。

由索引模型根据 Issue 内容生成。