Enhance delete methods in tests

[simitt]

Refactor current handling of deleting indices, template and policies, as it might be dangerous and can affect test parallelization.

quoting @urso from a conversation over this:

Normally for these kind of tests I use a mix of -- as a prefix. And this per test. Teardown cleans resources only on success, or always after dumping state to some files. But this also requires a few more changes to the beats configs I guess.

[botelastic]

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[botelastic]

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