Rerun submission when a task used is deleted

[ihsaan-ullah]

@ mention of reviewers

@Didayolo

A brief description of the purpose of the changes contained in this PR.

Previously, when a task was disconnected from a competition but it was used in a submission: Rerunning such submission would result in a submission stuck in submitted status.

Now, when task/tasks are deleted, a warning message is shown to the user:

If a user tries to rerun submission with its task deleted, the following error message is shown:

Issues this PR resolves

• Rerun submission after deleting a task #1179
• Problems with re-running submissions #1182 -> Re-run submission on deleted task

A checklist for hand testing

For single-task phase

• Create a competition with one task A per phase,
• upload a submission and wait for its success,
• add a new task B in resource interface
• remove task A from phase
• connect task B to this phase
• delete task A from resource interface
• rerun the submission and check if you get an error

For multi-task phase

• repeat the above but make sure to create multi-task phase

Checklist

• Code review by me
• Hand tested by me
• I'm proud of my work
• Code review by reviewer
• Hand tested by reviewer
• CircleCi tests are passing
• Ready to merge

[Didayolo]

Nice job!