Move to using interface for better mocking at chaoshub package

[namkyu1999]

Proposed changes

Currently, our Golang codebase heavily relies on concrete types for implementing functionality. It causes hard to make unit tests. So I propose an interface pattern for loose coupling like this PR. For this PR, I only targeted the chaoshub package. If this approach is correct. I will refactor all packages to the interface.

And last, The below variable will be deleted after all packages are refactored to the interface.

litmus/litmus-portal/graphql-server/pkg/database/mongodb/operations.go

Line 33 in 601da40

Operator MongoOperator = &MongoOperations{}

Issue No. #3931 #3892

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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)
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Dependency

• Please add the links to the dependent PR need to be merged before this (if any).

Special notes for your reviewer: @S-ayanide @amityt

[S-ayanide]

Clean code 🚀 Hub looks pretty refactored to me 🏆

[gdsoumya]

Minor comment, rest looks good

[gdsoumya]

LGTM! Thanks for the PR!