Improve Parsing for KV Format in tree explain. #15098

Describe the bug

part of #14914

While adding more complex physical plan explain format, here are some issues met while parsing format line: writeln!(f, "{}={}", key, value) into extra_info in render tree:

• Every line should only be kv format.
• If there is a \n inside the key or value, it must be treated as a new line.

To Reproduce

No response

Expected behavior

We need a more flexible parser.

Additional context

No response