[UI, #230] Implement undo delete test case functionality

[DanielRendox]

Description of changes made

• Rebased and updated the code from Implement undo delete test case functionality #411
• Fixed a minor bug

Closes #230

• I have checked that I am merging into correct branch

[github-actions]

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[stephanlukasczyk]

While I agree on the changes in general, one conceptual question, for which consider the following scenario:

I have generated tests and executed them. Now the "Run all" button is disabled (so far, so good). Afterwards, I delete one of the test cases (permanently, but does not matter IMHO). My assumption now was that I should be able to rerun the tests again, because presumably coverage might have changed. However, that is not possible, the button is still disabled.

IMHO allowing re-execution of the tests in such a scenario is independent of this PR, however, I would like to know, what do you think @DanielRendox @pderakhshanfar about activating the run buttons in such a case?

[DanielRendox]

@stephanlukasczyk Agreed, sounds reasonable