Improve flaky CI integration tests

[morazow]

Sometimes integration tests in CI fail with exception related to memory issues.

com.exasol.jdbc.ConnectionLost: Connection lost after system running out of memory. SessionID:1695300427049402368
[info]   at com.exasol.jdbc.ExceptionFactory.createSQLException(ExceptionFactory.java:154)
[info]   at com.exasol.jdbc.ExceptionFactory.createSQLException(ExceptionFactory.java:21)
[info]   at com.exasol.jdbc.AbstractEXAConnection.connectAndLogin(AbstractEXAConnection.java:2376)
[info]   at com.exasol.jdbc.AbstractEXAConnection.setupConnection(AbstractEXAConnection.java:1492)
[info]   at com.exasol.jdbc.AbstractEXAConnection.reconnect(AbstractEXAConnection.java:3813)
[info]   at com.exasol.jdbc.ServerCommunication.handle(ServerCommunication.java:230)
[info]   at com.exasol.jdbc.AbstractEXAConnection.communication(AbstractEXAConnection.java:2847)
[info]   at com.exasol.jdbc.AbstractEXAConnection.communication_resultset(AbstractEXAConnection.java:2553)
[info]   at com.exasol.jdbc.AbstractEXAStatement.execute(AbstractEXAStatement.java:466)
[info]   at com.exasol.jdbc.EXAStatement.execute(EXAStatement.java:288)
[info]   ...

Acceptance Criteria

• Importer tests are separated
• Sleeps are removed