[clang] [clang][ssaf] Implement JSONFormat (PR #180021)

[Balázs Benics via cfe-commits]

steakhal wrote:

So I asked Claude to create a libfuzzer harness for the readTUSummary and I had it running for a while with asan and UBsan let it run for a while with a custom dictionary. It didn't find any issues - no surprise given the coverage of your tests already. ✅ 

https://github.com/llvm/llvm-project/pull/180021