[llvm] [llvm][DebugInfo] Use formatv() instead of format() (PR #191308)

[Konrad Kleine via llvm-commits]

kwk wrote:

> I appreciate the instinct to make it a single change switchover, but this is a bit much in one go when it's all quite similar but not the same changes.
> 
> Perhaps you can split this at wherever @s-barannikov got to and make another PR with the rest?

@DavidSpickett yes, I'll try that. @s-barannikov thank you for your review so far. I'm running some tests locally but then I'll try to split things. If you don't mind I'd like to leave the changes to the tests in the first commit. Most of them exist to prove to the reviewer that the new `formatv` does the same as the `format` with a specific format string. I actually used it to construct the new format strings sometimes.

https://github.com/llvm/llvm-project/pull/191308