feat: add toJSONBytes method to JSONObject/JSONArray, for issue #3963

[jujn]

What this PR does / why we need it?

Summary of your change

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.