DNS Chaos - Format TargetHostnames String For dns_interceptor Binary

[aditya3103]

What this PR does / why we need it:

This PR creates a function under stringutils which takes comma separated targetHostnames string as input and return formatted string which is expected by dns_interceptor binary

This removes manual effort from the user to enter a string with correct formatting

For example

experiment.targetHostnames = "Alice, Bob, Charlie" (string entered by user)
FormatHostnames(experiment.targetHostnames) = "["Alice", "Bob", "Charlie"]" (as expected by dns_interceptor binary)

As of now the experiment fails when a comma separated string value is passed from ChaosCenter.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Checklist:

• Fixes #
• PR messages has document related information
• Labelled this PR & related issue with breaking-changes tag
• PR messages has breaking changes related information
• Labelled this PR & related issue with requires-upgrade tag
• PR messages has upgrade related information
• Commit has unit tests
• Commit has integration tests
• E2E run Required for the changes

[aditya3103]

• Moved validation to one level up - from helper binary to experiment binary
• Ensured backward compatibility by checking for JSON string initially
• Fallback method assumes comma separated string with appropriate error mechanism

[aditya3103]

@neelanjan00 @ispeakc0de
I have updated as per the suggestion !

Edit: Any updates @neelanjan00 ?