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

[via llvm-commits]

youngdfb wrote:

> is your intent to verify errors in the debug_names section? If so, you don't need to use assembly, it's possible to use a YAML format too, e.g.: llvm-project/llvm/unittests/DebugInfo/DWARF/DWARFAcceleratorTableTest.cpp

The idea of the test is to validate the JSON emitted from the LLVM-dwarfdump script invocation is correct as there was no existing test for that that I could find.
The specifics of the test file aren't super important; I simply copied from an existing because it was already set up with several errors that I could then see in the JSON.  Additionally, those types of errors, on missing names with different tags, is the extension I am looking to follow up with.  By either making keys more precise or adding a sub-breakdown under the category.  Hence a JSON output change that should have a test.  
Begs question of whether should be validating JSON for a clean DWARF, too to make sure JSON is empty.

The changes to modify JSON are in DWARFVerifier.h & llvm-project/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp I don't see a unit test setup for DWARFVerifier.

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