Add ability to get Output Partitions Count to ExecutionPlan.

[kylebrooks-8451]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I'd like to be able to get the number of output partitions from an ExecutionPlan. This is so I can use this to create Arrow Flight Tickets for a certain partition number.

Describe alternatives you've considered
No alternatives.

Additional context
This allows for using Substrait to serialize optimized logical plans along with a Partition number in an Arrow Flight Ticket. Then to Get method of Arrow Flight can only fetch a single partition.