[Bug fix] Add a format validation step before format conversion. (#36404)

This PR aims to fix the bug #35225 by introducing a new method IsJson to determine if a given text is in JSON format.
The IsJson method is then utilized in the ToJsonFromXmlOrCsvAsync method to optimize the processing logic.
If the text is already in JSON format, it is returned directly without further conversion from XML or CSV.

Co-authored-by: Heiko <61519853+htcfreek@users.noreply.github.com>

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Signed-off-by: Shawn Yuan <shuai.yuan.zju@gmail.com>
Co-authored-by: Heiko <61519853+htcfreek@users.noreply.github.com>