Remove hardcoded registry name for fault step when creating experiments from the UI

[Calvinaud]

Proposed changes

Remove hardcoded registry name when creating experiment from the UI #5197

• Updated both updateExperimentManifestWithFaultData and addFaultsToManifest to use experiment ImageRegistry
• Defaulting to litmuschaos if no ImageRestry find in experiment

Types of changes

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• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices applies)

Checklist

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• I have read the CONTRIBUTING doc
• I have signed the commit for DCO to be passed.
• Lint and unit tests pass locally with my changes
• [NA] I have added tests that prove my fix is effective or that my feature works (if appropriate)
• [NA] I have added necessary documentation (if appropriate)