Parallelize the tests as much as possible to reduce testing time

[ShreckYe]

See:

exposed-vertx-sql-client/integrated/src/test/kotlin/com/huanshankeji/exposedvertxsqlclient/integrated/TestsForAllRdbmsTypesAndAllClientTypesWithTestcontainers.kt

Lines 42 to 43 in 56dd325

	// This causes passing tests to fail. Not sure why.
	//testExecutionMode = TestExecutionMode.Concurrent

[ShreckYe]

A point I realized from #111

The side effects have to be isolated for tests to be parallelized. Tests for different DBs can easily be parallelized because they connect to different containers. If the lowest-level tests need to be parallelized, they need to create tables of different names.