chore: cleanup resources at startup

[kiraksi]

This PR:

• Uses prefixer function in conftest from python-test-utils to assign IDs to datasets in samples/snippets
• If dataset IDs already exist with the same name, those get deleted at start time
• Primarily, this ensures that any tests that are stopped or crash do not leave dataset resources behind

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Fixes#590 🦕

[chalmerlowe]

@kiraksi Per our discussion:

• please figure out whether we need individual mechanisms to create prefixes in our tests OR if we can rely upon the mechanisms in conftest to do it globally.

[chalmerlowe]

LGTM