Fix bug where passing existing experiment name into UpdateChaosExperiment causes error

[1spyral]

Fixes #5320

Proposed changes

Fetches the existing experiments with the declared experiment name and compares it with the experiment being edited. If they are the same, skip the duplicate name check which was previously erroring.

Changes to tests:

• Mock the fetch for the existing experiment
• Rename tests to use success and failure like other tests in file
• Add test to ensure that passing a duplicate experiment name throws an error

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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• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

[1spyral]

@SarthakJain26 thanks for the review! I've optimized the check to use one DB query. Let me know if everything looks good to you!

[1spyral]

Fixed outdated mocks in fuzz test

[SarthakJain26]

graphq-server build pipeline failing due to vulnerability scanning. Will fix the vulnerability in another PR.