[llvm] [VPlan] Match more GEP-like in m_GetElementPtr (PR #158019)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Do you plan to use this in a follow-up patch? Just wondering what the best way is to test this

I wasn't able to find other opportunities to use this, but wanted to fix the fact that we have a bad matcher. Added unit-test now.

https://github.com/llvm/llvm-project/pull/158019