Upstream libs and tools have improvements that make them unnecessary.

The failures are caused by the changes in PHP according to https://wiki.php.net/rfc/notice-for-non-valid-array-container.

1. Got rid of hard-coded exception mocks in favor of PHPUnit-generated ones where possible.
2. Reworked AbstractDriverTest::testConvertsException() to use a data provider to make testing all types of exceptions independent.
3. Updated PHPUnit since the reworked code relies on sebastianbergmann/phpunit#3604.

Refactored the logic of connection string generation

Fixes https://github.com/doctrine/dbal/issues/3114

As per @belgattitude's review.

Since the test is skipped when the driver is not an instance of
`VersionAwarePlatformDriver` we don't need to validate it again.

The message was a bit confusing as well (expected vs given).