The flip6 build profile only runs the Flip-6 related test cases. Moreover,
all Flip-6 related test cases are excluded when not running the flip6 build
profile. This should reduce testing time when adding more and more Flip-6
test cases.

Include flink-test-utils-junit in all submodules to make the Category marker interfaces Flip6 and OldAndFlip6 available

This closes #4889.

This closes #5263.

This closes #5213.

* Fix a scala example which is using a wrong variable
* Remove partitioning descriptions
  * partitioning parameters are already removed from
  IterativeStream#closeWith/DateStream#iterate
  * https://github.com/apache/flink/pull/988
  * https://github.com/apache/flink/pull/4655

This closes #5249.

This closes #5122.

This closes #5162.

This closes #5175.

This closes #5180.

This closes #5258.

This closes #5255.

While Buffer class is used in multithreaded context it requires synchronisation.
Previously it was miss-leading and unclear, suggesting that RecordSerializer should
take into account synchronisation of the Buffer that's holding. With NotThreadSafe
BufferBuilder there is now clear separation between single-threaded writing/creating
a BufferBuilder and multithreaded Buffer handling/retaining/recycling.

This increases throughput of network stack by factor of 2, because previously
method getMemorySegment() was called twice per record and it is a synchronized
method on recycleLock, while RecordSerializer is sole owner of the Buffer at
this point, so synchronisation is not needed.

Previously, the testScaleUp() test was taking too much resources and
causing test resources to be terminated before the test could finish.
This commit lowers the intensity of the test, while still retaining the
verified behaviour (i.e., when restoring the Kafka consumer with higher
parallelism and more Kafka partitions).

This closes #5201.

This closes #5193.

[FLINK-8268][streaming][tests] Improve TwoPhaseCommitSinkFunctionTest stability by using custom in memory storage

The previous link was referencing a non-existent constructor signature.

FlinkKafkaProducer010Configuration is the return type of the deprecated
writeToKafkaWithTimestamp factory methods. Therefore, the class should
also be deprecated as well.

This commit moves deprecated factory methods of the
FlinkKafkaProducer010 behind regular constructors, for better navigation
and readability of the code.

This closes #5179.

This closes #5121.

This makes it easier for users and contributors to figure out how
to create local file paths in way that works cross operating systems.

The input stream from ByteStreamStateHandle did not overwrite the 'read(byte[], int, int)' method,
meaning that bulk byte reads resulted in many individual byte accesses.

Additionally, this change avoids accessing the data array through an outer class, but instead adds
a reference directly to the input stream class, avoiding one hop per access. That also allows
a more restricted access level on the fields, which may additionally help the jitter in some cases.