[llvm] [GIsel][AArch64] Legalize <2 x i16> for G_INSERT_VECTOR_ELT (PR #65830)

[Amara Emerson via llvm-commits]

aemerson wrote:

> > Do we need to add `widenVectorEltsToVectorMinSize` to more vector operations?
> 
> Now only do the minimal fix type **v2s16**.

And why not do `widenVectorEltsToVectorMinSize()`?

https://github.com/llvm/llvm-project/pull/65830