[llvm] [RemoveDIs] Print non-intrinsic debug info in textual IR output (PR #79281)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> (because I haven't been keeping up with this work, what does the `P` in `DP` stand for?)

"Debug Program" - it's the term we used earlier on when our model for RemoveDIs was essentially a "shadow function" that duplicated the original function with placeholders instead of instructions ("debug program markers"), where all the debug info would be inserted (as "debug program values") instead of in the real function. We've changed our approach now, so we're also renaming the classes as part of a more general restructure to support dbg.labels (see: https://github.com/llvm/llvm-project/pull/78252) to have `DbgRecord` as the base class and `DbgValueRecord/DbgDeclareRecord/DbgAssignRecord` descending from that.

https://github.com/llvm/llvm-project/pull/79281