[Enhancement] Add an option to disable wrapping json to json array.

[wuxueyang96]

When inserting data like the below:

String[] records = new String[]{
        "[{\"id\":400, \"name\":\"400\"}]",
        "[{\"id\":500, \"name\":\"500\"}]"
};
DataStream<String> source = env.fromElements(records);

It fails since connector wrapped the json array into json array's array.

What type of PR is this：

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Which issues of this PR fixes ：

Fixes #

Problem Summary(Required) ：

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr will affect users' behaviors
• This pr needs user documentation (for new or modified features or behaviors)
• I have added documentation for my new feature or new function