[clang] [clang-repl] Implement value printing of custom types (PR #84769)

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

Hi @weliveindetail, I wanted to put in this PR which I am working from time to time on and will likely be very relevant for out-of-process execution. I still need to rebase it properly to the new "stuff" that landed recently. If you know how to rebase it faster, I would not mind some help...

Ideally, I'd like to implement a facility that aids interpreter-synthesized code. Right now the big ugliness is that we expose some API to the interpreter just to be able to send some code over codegen...

Another challenge is that we probably want to keep the stl type printing header slim and include only what we need from it. Perhaps looking if an include protector was defined only then include the related value printing primitives...

https://github.com/llvm/llvm-project/pull/84769