test: Integration test admin delete

[KIrie-0217]

Issue #, if available:
#143

Description of changes:
I have added the test for dy admin delete command.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[KIrie-0217]

During the execution of the destructor for TestManager tm, cleanup is performed on a table that has already been deleted, which causes an error.
To avoid this, the destructor's processing is skipped using std::mem::forget.
While this is not unsafe, the use of std::mem::forget may potentially lead to memory leaks in the future.

I would like you to evaluate whether this implementation is valid or not.

https://github.com/KIrie-0217/dynein/blob/integration-test-admin-delete/tests/admin_delete.rs#L64-L65

[StoneDot]

Thank you for adding tests for dy admin delete command. I left some comments. Could you please check them?

[StoneDot]

Thank you for polishing up the code. Now, LGTM. I left some comments for additional improvement. If you'd like to include them in this pull request, I'll check them after you change them.

[StoneDot]

I think added logic is reasonable. Could you remove the unused function count_temporary_tables?

[StoneDot]

Thank you for improving the pull request. All looks great to me.