Tests: Use the `default_storage_engine` MySQL option on newer MySQL versions.

In MySQL 5.5.3, `storage_engine` was deprecated in favour of `default_storage_engine`, and subsequently removed in MySQL 5.7. To avoid errors when running tests on MySQL 5.7, we need to switch between the options based on MySQL version.

Props skithund, jeremyfelt.

Fixes #34692.


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