Test: Add token controller operator related methods unit tests

[patitonar]

Context

Partial implementation of #346

Built on top of #684 to avoid conflicts in the setup

Changes proposed in this pull request

Adds new unit tests for:

• changeOperator()
• operatorTransfer()
• mint()
• burnFrom()

Test plan

New tests were added:

• test/unit/TokenController/changeOperator.js
• test/unit/TokenController/operatorTransfer.js
• test/unit/TokenController/mint.js
• test/unit/TokenController/burnFrom.js

Checklist

• Rebased the base branch
• Attached corresponding Github issue
• Prefixed the name with the type of change (i.e. feat, chore, test)
• Performed a self-review of my own code
• Followed the style guidelines of this project
• Made corresponding changes to the documentation
• Didn't generate new warnings
• Didn't generate failures on existing tests
• Added tests that prove my fix is effective or that my feature works

Review

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• 🍰 = Nice to have but not essential.
• 💡 = Suggestion or a comment based on personal opinion
• 🔨 = I believe this should be changed.
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• 🚀 = Feedback