ErrorSuppressionTest::testSuppressWarning(): refactor to data provider
ErrorSuppressionTest::testSuppressWarning(): refactor to data provider

* Maintains the exact same existing tests, now using a data provider.
    The data provider uses keys which allows for much more descriptive output when using the PHPUnit `--testdox` option, as well as for easier debugging if/when a test would fail.
* Orders the tests in logical groups in the data provider.
* Switches out `assertEquals()` (loose type comparison) for `assertSame()` (strict type comparison).
* Caches the `$config` and `$ruleset` for the test via static local variables to prevent the test run from becoming slower due to the change to the data provider.

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