MINOR: Fix MiniKdc Java 17 issue in system tests (#14011)

Kafka system tests with Java version 17 are failing on this issue:

```python
TimeoutError("MiniKdc didn't finish startup",)
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/ducktape/tests/runner_client.py", line 186, in _do_run
    data = self.run_test()
  File "/usr/local/lib/python3.6/site-packages/ducktape/tests/runner_client.py", line 246, in run_test
    return self.test_context.function(self.test)
  File "/usr/local/lib/python3.6/site-packages/ducktape/mark/_mark.py", line 433, in wrapper
    return functools.partial(f, *args, **kwargs)(*w_args, **w_kwargs)
  File "/opt/kafka-dev/tests/kafkatest/sanity_checks/test_verifiable_producer.py", line 74, in test_simple_run
    self.kafka.start()
  File "/opt/kafka-dev/tests/kafkatest/services/kafka/kafka.py", line 635, in start
    self.start_minikdc_if_necessary(add_principals)
  File "/opt/kafka-dev/tests/kafkatest/services/kafka/kafka.py", line 596, in start_minikdc_if_necessary
    self.minikdc.start()
  File "/usr/local/lib/python3.6/site-packages/ducktape/services/service.py", line 265, in start
    self.start_node(node, **kwargs)
  File "/opt/kafka-dev/tests/kafkatest/services/security/minikdc.py", line 114, in start_node
    monitor.wait_until("MiniKdc Running", timeout_sec=60, backoff_sec=1, err_msg="MiniKdc didn't finish startup")
  File "/usr/local/lib/python3.6/site-packages/ducktape/cluster/remoteaccount.py", line 754, in wait_until
    allow_fail=True) == 0, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/ducktape/utils/util.py", line 58, in wait_until
    raise TimeoutError(err_msg() if callable(err_msg) else err_msg) from last_exception
ducktape.errors.TimeoutError: MiniKdc didn't finish startup
```

Specifically, when one runs the test cases and looks at the logs of the MiniKdc:
```java
Exception in thread "main" java.lang.IllegalAccessException: class kafka.security.minikdc.MiniKdc cannot access class sun.security.krb5.Config (in module java.security.jgss) because module java.security.jgss does not export sun.security.krb5 to unnamed module @24959ca4
    at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:392)
    at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:674)
    at java.base/java.lang.reflect.Method.invoke(Method.java:560)
    at kafka.security.minikdc.MiniKdc.refreshJvmKerberosConfig(MiniKdc.scala:268)
    at kafka.security.minikdc.MiniKdc.initJvmKerberosConfig(MiniKdc.scala:245)
    at kafka.security.minikdc.MiniKdc.start(MiniKdc.scala:123)
    at kafka.security.minikdc.MiniKdc$.start(MiniKdc.scala:375)
    at kafka.security.minikdc.MiniKdc$.main(MiniKdc.scala:366)
    at kafka.security.minikdc.MiniKdc.main(MiniKdc.scala)
```

This error is caused by the fact that sun.security module is no longer supported in Java 16 and higher. Related to the [1]. 
There are two ways how to solve it, and I present one of them. The second way is to export the ENV variable during the deployment of the containers using Ducktape in [2].

[1] - https://openjdk.org/jeps/396
[2] - https://github.com/apache/kafka/blob/trunk/tests/docker/ducker-ak#L308

Reviewers: Ismael Juma <ismael@juma.me.uk>, Luke Chen <showuon@gmail.com>

tests/kafkatest/services/security/minikdc.py

@@ -107,6 +107,8 @@ class MiniKdc(KafkaPathResolverMixin, Service):
         cmd = "for file in %s; do CLASSPATH=$CLASSPATH:$file; done;" % core_libs_jar
         cmd += " for file in %s; do CLASSPATH=$CLASSPATH:$file; done;" % core_dependant_test_libs_jar
         cmd += " export CLASSPATH;"
+        # avoids java.lang.IllegalAccessException due to usage of internal `sun.security.krb5.Config` in `MiniKdc`
+        cmd += " export KAFKA_OPTS=\"--add-exports java.security.jgss/sun.security.krb5=ALL-UNNAMED\";"
         cmd += " %s kafka.security.minikdc.MiniKdc %s %s %s %s 1>> %s 2>> %s &" % (self.path.script("kafka-run-class.sh", node), MiniKdc.WORK_DIR, MiniKdc.PROPS_FILE, MiniKdc.KEYTAB_FILE, principals, MiniKdc.LOG_FILE, MiniKdc.LOG_FILE)
         self.logger.debug("Attempting to start MiniKdc on %s with command: %s" % (str(node.account), cmd))
         with node.account.monitor_log(MiniKdc.LOG_FILE) as monitor: