refactor: Update prefix logic in DA

[Aditya-ranjan-16]

Description

Updated the code logic of prefix variable such that it allows prefix to be "" (empty string) for advanced users. Also, added default value(dev) for prefix and marked as required in catalog manifest.

#11959

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Release notes content

Adds the default value for prefix variable and mark as required in catalog manifest. Also allows prefix to be "" (empty string ).

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[Aditya-ranjan-16]

/run pipeline

[iamar7]

Instead of checking for null & empty strings everywhere like this -> (var.prefix != null && var.prefix != "").

Could you please use the same method as in this PR?