[llvm] [llvm-readobj][ELF] Implement JSON output for --dynamic-table (PR #95976)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM now, with a couple of nits. Just don't forget to update the commit message before merging.

Would you be okay to do a (hopefully) small follow-up change to tidy up the slightly weird LLVM output, where it is using lists for single-item elements, please?

https://github.com/llvm/llvm-project/pull/95976