arrow

ARROW-9821: [Rust][DataFusion] Support for User Defined ExtensionNodes in the LogicalPlan

This PR is based on the prototype design in https://github.com/apache/arrow/pull/8020 and the discussion in the [Design Document](https://docs.google.com/document/d/1IHCGkCuUvnE9BavkykPULn6Ugxgqc1JShT4nz1vMi7g/edit#) and the [discussion on the mailing list](https://lists.apache.org/thread.html/rf8ae7d1147e93e3f6172bc2e4fa50a38abcb35f046cc5830e09da6cc%40%3Cdev.arrow.apache.org%3E). See also https://issues.apache.org/jira/browse/ARROW-9821,

This PR adds:
1. A `ExtensionNode` trait for defining user defined behavior in LogicalPlanNodes
2. Support for planning (both logical and physical) for such plan nodes
3. An end to end example and test of using LogicalPlanNode to implement a simple "topK" operator using a custom defined plan node.

The idea of the end to end example is both to serve as documentation as well as to ensure the API can be used for a non trivial example operator

Major Differences from the prototype:
1. Renamed `LogicalPlanNode` to `ExtensionPlanNode` as I think that better reflects what it is
2. I did not change the built in `LimitNode` to use the new interface, but instead created an end-to-end demonstration
3. Demonstration of how to provide a custom physical planner (per comment https://github.com/apache/arrow/pull/8020#discussion_r475953168 from @andygrove)
3. The code for `Extension` plan node is less of a mess (uses `Arc` instead of `Box`)
4.  Register the new optimization passes so that the high level `ExecutionContext::sql` could be used rather than the low level APIs.

I am sorry for the relatively large PR -- most of the code is the new example with comments.

I can also break this into a few smaller PRs (the changes to `ExecutionConfig` and `DefaultPhysicalPlanner` could naturally be broken out, if that would be easier)

Closes #8097 from alamb/alamb/ARROW-9821-user-defined-api

Authored-by: alamb <andrew@nerdnetworks.org>
Signed-off-by: Andy Grove <andygrove73@gmail.com>