[clang] [clang][ssaf] Add `JSONFormat` support for `TUSummaryEncoding` (PR #183401)

[Balázs Benics via cfe-commits]

https://github.com/steakhal commented:

I did a thorough review and basically everything looks right.
I've spotted some anomalies in other parts that I think we should fix in a followup PR, but otherwise it's great.

For the rest of the comments, I'm confident that it would take you less than 5 minutes to fix.

https://github.com/llvm/llvm-project/pull/183401