MINOR: Cleanup Core Module- Scala Modules (1/n)

[sjhajharia]

Now that Kafka Brokers support Java 17, this PR makes some changes in
core module. The changes in this PR are limited to only the Scala files
in the Core module's tests. The unit tests module is still pending. It
shall follow next. The changes mostly include:

• Collections.emptyList(), Collections.singletonList() and
  Arrays.asList() are replaced with List.of()
• Collections.emptyMap() and Collections.singletonMap() are replaced
  with Map.of()
• Collections.singleton() is replaced with Set.of()

To be clear, the directories being targeted in this PR are:

• core/src/test/scala/kafka
• core/src/test/scala/integration/kafka

[sjhajharia]

OffloadAndTxnConsumeFromLeaderTest -> Seems to be a flaky test

[m1a2st]

Hello @sjhajharia, Thanks for this PR. I found there are some Collections related not modified on your branch. Could you take a look.

[sjhajharia]

Hey @m1a2st
Thanks for the checks. Yes you are correct, this PR doesnt handle all the Scala files at once. (I tried to take a rough estimate and it was way over 125 files).
This is the first PR in the series and this targets just the code in the integration tests folder. This shall be followed by changes in the unit tests folder and then finally the main code folder.
Let me update the PR title to 1/n

[m1a2st]

Thanks @sjhajharia for this patch, left some comments.

Could you check all scala code which use asJava to transfer Scala collection to Java collection, We can avoid to use both collection in same file.
And also update util.Arrays.asList to java.util.List.of.

[sjhajharia]

Thanks @m1a2st for the comment.
I had eliminated all the asList cases. The conversions to asJava was a good bird to target as well. Thanks for the suggestion. I have updated the PR accordingly (and have thus added many more files).

To be clear, the directories being targeted in this PR are:

• core/src/test/scala/kafka
• core/src/test/scala/integration/kafka