[clang] [clang] Allow devirtualisation of indirect calls to final virtual methods (PR #165341)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

Ok, I've added multiple and virtual inheritance tests, and included tests that force static and dynamic this adjustments.

We currently do not appear to devirtualise dynamic this adjustments, which means the tests currently use the vtable to perform dynamic this adjustments, and then immediately inline the virtual functions \o/

https://github.com/llvm/llvm-project/pull/165341