BeamSQL aggregation analytics functionality

Mentor email: ruwang@google.com. Feel free to send emails for your questions.

Project Information
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BeamSQL has a long list of of aggregation/aggregation analytics functionalities to support.

To begin with, you will need to support this syntax:

```

analytic_function_name ( [ argument_list ] )
OVER (
[ PARTITION BY partition_expression_list
]
[ ORDER BY expression [{ ASC | DESC }] [, ...] ]
[ window_frame_clause ]
)

```

As there is a long list of analytics functions, a good start point is support rank() first.

This will requires touch core components of BeamSQL:
1. SQL parser to support the syntax above.
2. SQL core to implement physical relational operator.
3. Distributed algorithms to implement a list of functions in a distributed manner.
4. Enable in ZetaSQL dialect.

To understand what SQL analytics functionality is, you could check this great explanation doc: https://cloud.google.com/bigquery/docs/reference/standard-sql/analytic-function-concepts.

To know about Beam's programming model, check: https://beam.apache.org/documentation/programming-guide/#overview

Imported from Jira [BEAM-9198](https://issues.apache.org/jira/browse/BEAM-9198). Original Jira may contain additional context.
Reported by: amaliujia.