[llvm] [DwarfDump] Add new set of line-table-related statistics to llvm-dwarfdump (PR #93289)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> Since this adds new stats, I suppose the schema on LNT may need to be updated... Perhaps @adrian-prantl can help with that once this merges.

My assumption at the moment would be that this is passed through as JSON, s.t. new fields will be ignored by default - so it shouldn't cause any problems at least for the existing stats, though it would be good to get these added!

Without getting ahead of things too much (I'll have a discourse post soon going more into the topic), it looks as though the unique lines metric has been degrading in clang over time, so it'd be good to get some continuous measurement.

https://github.com/llvm/llvm-project/pull/93289