Use DB_CLOSE_ON_EXIT=FALSE for H2 DevServices

To avoid metaspace leaks when H2 registers one shutdown hook each
time we start it: the shutdown hook indirectly references a
QuarkusClassLoader of its corresponding application startup,
which references loads of Quarkus and application classes and
prevents them from being garbage collected, which ultimately leads to
OutOfMemoryError: Metaspace.

This impacts devmode in particular.

extensions/devservices/h2/src/main/java/io/quarkus/devservices/h2/deployment/H2DevServicesProcessor.java

@@ -61,7 +61,7 @@ public RunningDevServicesDatasource startDatabase(Optional<String> username, Opt
 
                     String connectionUrl = "jdbc:h2:tcp://localhost:" + tcpServer.getPort() + "/mem:"
                             + effectiveDbName
-                            + ";DB_CLOSE_DELAY=-1" + additionalArgs.toString();
+                            + ";DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE" + additionalArgs;
                     return new RunningDevServicesDatasource(null,
                             connectionUrl,
                             null,