[llvm] Add test for dwarf verification JSON output (PR #124936)

[via llvm-commits]

youngdfb wrote:

This test is basically a copy of 
https://github.com/llvm/llvm-project/blob/main/llvm/test/tools/llvm-dwarfdump/X86/debug-names-verify-completeness.s
but we have the llvm-dwarfdump command emit JSON and then validate the JSON and be sure a line from raw output is not in JSON.

https://github.com/llvm/llvm-project/pull/124936