This updates the Row.toString method to provide a good summary string.

In particular it fixes the following issues:

Changeflag: According to FLIP-95, a row describes an entry in a
changelog. Therefore, it should visible whether a row is an insert,
delete, or update change. Now indicated with +I, -D, +U, -U.

Nested rows: In the old implementation it was not visible whether nested
rows exist or not due to missing start/end boundaries. Now indicated with
[...] or {...}.

Positioned rows vs. named rows: According to FLIP-136, it should be visible
whether a row operates in name-based or position-based field mode. Now
indicated with [...] or {...}.

Nested arrays in maps and lists: In the old implementation arrays in maps
or lists could not be represented.

Wrong formatting: Most programming languages use a space after a comma.

This is an incompatible change. If the legacy representation is still
required for tests, the old behavior can be restored via the flag
RowUtils.USE_LEGACY_TO_STRING for the local JVM. However, relying on
the row's string representation for tests is not a good idea in general as
field data types are not verified.

[FLINK-20738][table-planner-blink] Introduce BatchPhysicalPythonGroupAggregate, and make BatchExecPythonGroupAggregate only extended from ExecNode

This closes #14562

[FLINK-20738][table-planner-blink] Introduce BatchPhysicalLocalSortAggregate, and make BatchPhysicalLocalSortAggregate only extended from FlinkPhysicalRel

This closes #14562

[FLINK-20738][table-planner-blink] Introduce BatchPhysicalSortAggregate, and make BatchExecSortAggregate only extended from ExecNode

This closes #14562

[FLINK-20738][table-planner-blink] Introduce BatchPhysicalLocalHashAggregate, and make BatchPhysicalLocalHashAggregate only extended from FlinkPhysicalRel

This closes #14562

[FLINK-20738][table-planner-blink] Introduce BatchPhysicalHashAggregate, and make BatchExecHashAggregate only extended from ExecNode

This closes #14562

[FLINK-20738][table-planner-blink] Rename BatchExecGroupAggregateBase to BatchPhysicalGroupAggregateBase and do some refactoring

This closes #14562

This adds an ITCase because we need to check that all the components
work together and that the wiring works correctly.

This uses the previously added funtionality to specify that given inputs
should be processed before other inputs and should not be sorted.

This doesn't change the actual behavior, we still set the same "sorted"
setting on both inputs. We will add tests and actually change the
behavior in a follow-up commit.

We allow the operation but it is a no-op because there never is any
keyed state because we process all broadcast input before starting to
process the keyed/other side.

This will allow processing the broadcast side of a broadcast operator
first, before processing the keyed side that requires sorting for
stateful BATCH execution.

For now, the wiring from the API is not there, this will be added in
follow-up changes.

Note: Broadcast operations in BATCH mode don't yet work with this
change. This needs follow-up changes from later commits. We just lay the
groundwork here and keep the same functionality.

Before, we were creating operators in BroadcastConnectedStreams eagerly.
Now, the transformation holds the user function and we add a Translator
that creates the "physical" operators when translating the graph of
Transformations.

We do this so that we can translate differently based on whether we're
in BATCH or STREAMING mode.

Because that's what it does.

[FLINK-20766][table-planner-blink] Introduce BatchPhysicalSortLimit, and make BatchExecSortLimit only extended from ExecNode

This closes #14502

[FLINK-20766][table-planner-blink] Introduce BatchPhysicalSort, and make BatchExeSort only extended from ExecNode

This closes #14502

[FLINK-20766][table-planner-blink] Introduce StreamPhysicalTemporalSort, and make StreamExecTemporalSort only extended from ExecNode.

This closes #14502

[FLINK-20766][table-planner-blink] Introduce StreamPhysicalSortLimit, and make StreamExecSortLimit only extends from ExecNode.

This closes #14502

[FLINK-20766][table-planner-blink] Introduce StreamPhysicalSort, and make StreamExecSort only extended from ExecNode

This closes #14502

[FLINK-20782][table-planner-blink] Introduce BatchPhysicalRank, and make BatchExecRank only extended from ExecNode

This closes #14506

In particularly, if task is idling forever, as there are no new records incomming
previous version would report idleTime as 0% and busyTime as 100% which is incorrect.

In this version, idleTime metric is aware that idling period has started and can take
that into account when updating it's value.

It's defined as inverted value of idleTimeMsPerSecond

This closes #14467

This closes #14563

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalPythonGroupTableAggregate, and make StreamExecPythonGroupTableAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalGroupTableAggregate, and make StreamExecGroupTableAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalIncrementalGroupAggregate, and make StreamExecIncrementalGroupAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalGlobalGroupAggregate, and make StreamExecGlobalGroupAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalLocalGroupAggregate, and make StreamExecLocalGroupAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalPythonGroupAggregate, and make StreamExecPythonGroupAggregate only extended from ExecNode

This closes #14478

[FLINK-20737][table-planner-blink] Introduce StreamPhysicalGroupAggregate, and make StreamExecGroupAggregate only extended from ExecNode

This closes #14478