Wall-Clock based Windowing / Suppression

[eichingertim]

The change adds the possibility to suppress events during windowing based on WALL_CLOCK_TIME instead of STREAM_CLOCK_TIME.

Problem Statement:
In our use case we needed this functionality, as the amount of events varies very much. Sometimes we get so few events, that the event won't be emitted at all unless a new event comes in to advance STREAM_CLOCK_TIME.

Solution:
We implemented a new possibility to use WALL_CLOCK_TIME instead of STREAM_CLOCK_TIME for suppression during windowing. It is based on a scheduled operation and punctuates the clock on each interval.

Testing:
For testing we extended the streams/src/test/java/org/apache/kafka/streams/kstream/internals/SuppressScenarioTest.java with a new scenario where the suppression is based on wall clock time.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)