[FLINK-15577][table-planner] Fix similar aggregations with different windows being considered the same

[BenoitHanotte]

What is the purpose of the change

The RelNode's digest is used by the Calcite HepPlanner to avoid adding
duplicate vertices to the graph. If an equivalent vertex was already
present in the graph, then that vertex is used in place of the newly
generated one.
This means that the digest needs to contain all the information
necessary to identifying a vertex and distinguishing it from similar (but not equivalent) vertices.

In the case of the WindowAggregation nodes, the window specs are
currently not in the digest, meaning that two aggregations with the same
signatures and expressions but different windows are considered
equivalent by the planner, which is not correct and will lead to an
invalid Physical Plan.

This commit fixes this issue and adds a test ensuring that the window
specs are in the digest, as well as similar aggregations on two
different windows will not be considered equivalent.

Brief change log

Added window specs to the following RelNodes:

• LogicalWindowAggregate
• FlinkLogicalWindowAggregate
• LogicalWindowTableAggregate
• FlinkLogicalWindowTableAggregate

Added unit tests to the legacy planner and the blink planner to prevent future regressions.

Verifying this change

This change added tests and can be verified as follows:

• Added unit tests for the old planner to ensure window specs are in digest and that similar aggregations with different windows are not considered equivalent in the physical plan.
• Added unit tests for the blink planner to ensure no such regression can be introduced in the future.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable